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Dr. Kennedy's Vocabulary Course: -A-
(View Course for 11/18/2013)
(A B C D E F G H I J K L M)
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Ron Kennedy, M.D.
Vocabulary Search:Phrase  Any Words

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(A B C D E F G H I J K L M)
Aaron's Rod:  (Used as a symbol for medicine.) A rod (walking stick) with one serpent twined around it, thus differing from Mercury's Caduceus (also used as a symbol of medicine), which has two serpents twined about it. The allusion is to the rod God gave to Moses and his brother Aaron with which to perform miracles and free the Israelites from bondage in Egypt. In the first miracle the rod changed into a serpent in front of Pharaoh. (Unfortunately, Pharaoh didn't give a rip.)
Abacterial thrombotic endocarditis:  Lesions inside the heart occurring with blood clots and inflammation of the wall of the heart in the terminal stages of many chronic infectious and wasting diseases. Synonyms are nonbacterial thrombotic endocarditis, cachectic endocarditis, terminal endocarditis, and thromboendocarditis.
Abadie's sign of tabes dorsalis:  Insensibility to pressure on the Achilles tendon. (Joseph Abadie: French neurosurgeon, 1873-1946) (Achilles: Mythical Greek warrior, vulnerable only at the heel). Tabes: Progressive emaciation of the body, accompanied with fever, with no discoverable cause. Tabes dorsalis: A condition that results from the destruction of the dorsal columns in the spinal cord which are responsible for proprioception (position sense). Loss of position sense causes severe gait and leg ataxia (balance and motor control problems). Tabes dorsalis can be the result of spinal cord injury or infection with syphilis. Tabes dorsalis results in a staggering wide-based gait, postural instability, pain and paresthesias. Tabes dorsalis is a classical sign of late stage syphilis, a condition which was once common but now rarely seen since the discovery of penicillin and methods to detect early syphilis.
Abasia:  Lack of motor or muscular coordination in walking.
Abasia trepidans:  Difficulty standing (abasia) due to trembling of the lower limbs.
Abbokinase:  A thrombolytic (clot busting) agent which works by activating the body's own fibrinolytic system by activating the production of plasmin from plasminogen. Plasmin is an enzyme which degrades fibrin clots and fibrinogen, as well as several other protein clotting factors.
Abbott's method:  A method of treatment of scoliosis (a curvature of the spine) by use of a series of plaster jackets applied after partial correction of the curvature by external force.
Abdomen:  The portion of the body which lies between the thorax and the pelvis. It contains a cavity (abdominal cavity) separated by the diaphragm from the thoracic cavity above and by the plane of the pelvic inlet from the pelvic cavity below and lined with a serous membrane, the peritoneum. This cavity contains the abdominal viscera and is enclosed by a wall formed by the abdominal muscles, vertebral column and the iliac bones on each side.
Abdominal angina:  A dull, cramping centralized abdominal pain that occurs 15-30 minutes after a meal, associated with ischemic bowel disease, and diagnosed with mesenteric arteriography.
Abdominal aortic aneurysm:  A weakened distended area in the wall of the abdominal aorta, more common in those who suffer from atherosclerosis. Rupture of an abdominal aortic aneurysm is usually fatal.
Abdominal apoplexy:  Bleeding, blood clot, or embolus in the vessels (arterial system) which supplies the intestine. Usually acutely painful.
Abdominal ballottement:  Examination of the abdomen by palpation to detect excessive amounts of fluid (ascites) by causing organs to bob up and down in the fluid milieu.
Abdominal dropsy:  An effusion and accumulation of serous fluid in the abdominal cavity, also called ascites.
Abdominal fistula:  A tract leading from one of the abdominal viscera to the external surface.
Abdominal migraine:  Migraine in children accompanied by paroxysmal abdominal pain. This must be distinguished from similar symptoms requiring surgical attention.
Abdominal muscle deficiency syndrome:  Congenital absence (partial or complete) of abdominal muscles, in which the outline of the intestines is visible through the protruding abdominal wall.
Abdominal paniculectomy:  A surgical procedure to remove fatty tissue and excess skin from the lower to middle portions of the abdomen. This procedure is indicated in some individual's who have lost considerable weight resulting in loose hanging folds of skin in the abdominal area. Recovery is in 2-4 days.
Abdominal pregnancy:  The implantation and development of the ovum in the peritoneal cavity, usually secondary to an early rupture of a tubal pregnancy; very rarely, primary implantation may occur in the peritoneal cavity.
Abdominal respiration:  Breathing effected mainly by the action of the diaphragm to the relative exclusion of the chest muscles.
Abdomino-jugular reflex:  An elevation of venous pressure visible in the jugular veins and measurable in the veins of the arm, produced in active or impending congestive heart failure by firm pressure with the flat hand over the abdomen. Often called hepato-jugular reflex when pressure is exclusively over the liver.
Abdominocentesis:  Paracentesis (aspiration of fluid using a needle) of the abdomen.
Abdominocyesis:  Pregnancy with implantation in the abdominal cavity.
Abdominoplasty:  A procedure to remove fatty tissue, excess skin and tighten the muscular and fascial structures of the lower to middle portions of the abdomen.
Abdominous:  Having a protuberant belly; pot-bellied.
Abduct:  To move away from the median plane.
Abelson murine leukemia virus:  A retrovirus belonging to the Type C retrovirus group subfamily (family Oncovirinae) which is associated with leukemia and produces in vitro transformation of mouse cells. (murine Pertaining to mice.) (in vitro In a test tube as distinguished from in a body which is in vivo.)
Abembryonic:  The area of the blastocyst opposite the region where the embryo is formed. In other words, the location of the developing placenta.
Abenteric:  Away from the intestine, said of a morbid process occurring elsewhere that would normally occur in the intestine.
Aberrant artery:  Artery having an unusual origin or course.
AbiologicaL:  Pertaining to the study of inanimate things.
Abiotic:  Refers to nonliving objects, substances or processes.
Abiotic stress:  Nonliving environmental factors (such as drought, extreme cold or heat, high winds) that can have harmful effects on animals or plants.
Abiotic transformation:  Any process in which a chemical in the environment is altered by non-biological mechanisms (such as by exposure to sunlight).
Abirritant:  A medicine that diminishes irritation.
Ablate:  To remove, usually by cutting. at surgery; e.g. a tumour can be "ablated."
Ablepharia:  Congenital absence, partial or complete, of the eyelids; recessive inheritance.
ABO antigens:  A system of genetically determined antigens (proteins) located on the surface of the erythrocyte. Blood type classifications are derived from these proteins.
ABO blood group:  The major human blood type system which describes the oligosaccharide glycoprotein antigens found on the surface of human blood cells. According to the type of antigen present, a person may be assigned a blood type of A, B, AB or O. A second type of antigen, the Rh factor, renders a positive or negative blood type. The ABO blood group system is important because it determines who can donate blood to or accept blood from whom. Type A or AB blood will cause an immune reaction in people with type B blood and type B and AB blood will cause a reaction in people with type A blood. Conversely, type O blood has no A or B antigens, so people with type O blood are universal donors. And since AB blood already produces both antigens, people who are type AB can accept any of the other blood types without suffering an immune reaction. They are termed universal recipients.
ABO hemolytic disease of the newborn or erythroblastosis fetalis:  due to maternal-fetal incompatibility with respect to an antigen of the ABO blood group; the fetus possesses A or B antigen which is lacking in the mother, and the mother produces immune antibody which causes hemolysis of fetal red blood cells.
ABO incompatibility:  A type of blood incompatibility, found rarely. Transfusion reactions may occur as a result of such incompatibility
Aborad:  In a direction away from the mouth; opposite of orad.
Aborticide:  The act of destroying a fetus in the womb; feticide. Also that which produces an abortion; aka abortifacient.
Abortifacient:  A drug or compound that induces the expulsion of an embryo or fetus.
Abortus:  Any product (or all products) of an abortion.
Abortus bacillus:  Brucella abortus A species of bacteria whose natural hosts are cattle and other bovidae. Other mammals, including man, may be infected. Abortion and placentitis are frequently produced in the pregnant animal.
Aboulia:  1. Loss or impairment of the ability to perform voluntary actions or to make decisions. 2. Reduction in speech, movement, thought, and emotional reaction; a common result of bilateral frontal lobe disease. Synonym: abulia. Origin: G. A-loss or absence + boule, will
Abrachia:  Congenital absence of arms.
abreact:  1. To show strong emotion while reliving a previous traumatic experience. 2. To discharge or release repressed emotion.
abreaction:  A process in psychotherapy in which the patient is "desensitised" to emotionally painful, often forgotten (repressed) memories by recalling and reacting to them in the "safety" of the treatment setting.
abruptio placentae:  This is the premature separation of the placenta, i.e. Separation of the placenta from the site of implantation on the uterus before the delivery of the fetus. It is a life threatening condition for the foetus and occurs about 1 in 500 to 750 deliveries.
absence seizure:  A type of seizure that in contrast to the grand mal seizure, is noted for its brevity and degree of loss of awareness (brief staring spell) accompanied by minimal motor manifestations. A common form of childhood epilepsy.
absent state:  The semiconscious state associated with an epileptic attack.
absolute agraphia:  Agraphia (inability to write) in which not even unconnected letters can be written.
absolute alcohol:  pure, anhydrous (containing no water) alcohol,
absolute glaucoma:  The final stage of blindness in glaucoma.
absolute zero:  The lowest possible temperature (0 Kelvin, -273.15 degrees Celsius, -459.67 degrees Fahrenheit). at this temperature, all molecular motion stops.
absolutist:  One who believes that it is possible to realize a cognition or concept of the absolute.
absorbable surgical suture:  A surgical suture material prepared from a substance that can be digested by body tissues and is therefore not permanent.
absorptive cells of intestine:  Cells on the surface of villi of the small intestine and the luminal surface of the large intestine that are characterized by having microvilli on their surfaces.
abstinence syndrome:  A constellation of physiologic changes undergone by persons who have become physically dependent on a drug or chemical due to prolonged use at elevated doses, but who are abruptly deprived of that substance.
acanthamoeba:  A microscopic organism, an amoeba, found in soil, dust and fresh water (lakes, rivers, hot springs and hot tubs). Infection can have dire consequences Lungs, eye, skin and brain can be affected. Brain involvement is fatal.
acapnia:  Less than the normal level of carbon dioxide in the blood. The opposite of hypercapnia. It comes from the [Greek ”a-” meaning ”without“ + ”kapnos“ meaning ”smoke“ so acapnia literally means ”smokeless“ referring to carbon dioxide which is a principal part of smoke.]
accessory nerve:  The accessory nerve is the eleventh cranial nerve. and supplies the sternocleidomastoid and trapezius muscles. Paralysis of the accessory nerve prevents rotation of the head away from that side and causes drooping of the shoulder.
accessory placenta:  An extra placenta separate from the main placenta. The placenta is the organ joining the mother and fetus, the organ that permits the provision of oxygen and nutrients to the fetus and the release of carbon dioxide and waste products from the fetus to the mother. The placenta and the fetal membranes are the afterbirth.
Acclimatization to altitude:  Altitude sickness is caused by going too high too fast. A healthy cardiovascular system can adapt to decreased oxygen concentration a process known as acclimatization. Changes take place in the body to allow it to operate with decreased oxygen: (1) Depth of respiration increases, (2) Pressure in the pulmonary arteries increases, forcing blood into portions of the lung which are normally not used at sea level, (3) More red blood cells to carry oxygen, (4)We make more of a specific substance (called 2,4-DPG) that facilitates the release of oxygen from hemoglobin to the body tissues. Acclimatization generally takes 1 to 3 days at a given altitude. For example, if a person hikes to 10,000 feet (3,048 meters) and spends several days at that altitude, her or his body acclimatizes to 10,000 feet (3,048 meters). If the person then climbs to 12,000 feet (3,658 meters), the body needs to acclimatize once again and it takes another 1 to 3 days.
Accommodation:  In medicine, the ability of the eye to change its focus from distant to near objects (and vice versa). This process is achieved by the lens changing its shape. Difficulty performing this feat usually sets in around age 45-55 and is known as "presbyopia," literally old vision. Old vision is corrected with reading glasses which replace the lens adjustment made in younger eyes. People who have myopia (nearsightedness) are sometimes spared presbyopia because they focus too close to start with and do not depend on accommodation for near vision.
ACE (angiotensin converting enzyme):  The angiotensins are peptides (substances smaller than proteins) that act as vasoconstricting agents (causing blood vessels to narrow). Narrowing the diameter of the blood vessels sends up the blood pressure. ACE converts angiotensin to its activated form (called angiotensin II) enabling it to function. The ACE inhibitors are drugs that inhibit the formation of angiotensin II and are used for blood pressure control and congestive heart failure.
Acellular:  Not made up of cells or divided into cells. Or lacking intact cells as, for example, an acellular vaccine which may contain cellular material but not complete cells.
Acentric chromosome:  A fragment of a chromosome (one of the microscopically visible carriers of the genetic material DNA) that is lacking a centromere (the ”waist“ of the chromosome essential for the division and the retention of the chromosome in the cell) and so is lost when the cell divides.
Aceruloplasminemia:  A genetic disorder in which there is absence of the protein ceruloplasmin from blood and accumulation of iron in the pancreas, liver and brain, causing diabetes and progressive neurodegeneration with the tremors and gait abnormalities characteristic of Parkinson disease. Ceruloplasmin normally removes iron from cells. The absence of ceruloplasmin leads to the abnormal deposition of iron in cells, including those of the pancreas, liver, retina and the basal ganglia region of the brain. The iron deposition damages these tissues and leads to the clinical features of the disease which usually appear between 30 and 50 years of age. Aggressive treatment with desferoxamine, a chelating agent that takes up iron, may halt the progression of these complications. Aceruloplasminemia is caused by mutations in the gene encoding ceruloplasmin.
Acetabulum:  the cup-shaped socket of the hip joint. The head (upper end) of the femur (the thighbone) fits into the acetabulum and articulates with it, forming a ball-and-socket joint. The word ”acetabulum“ in Latin means "cup."
Acetaminophen:  A non-aspirin analgesic
Acetone:  In the body, a chemical that is formed when the body uses fat instead of glucose (sugar) for energy. The formation of acetone means that cells lack insulin or cannot effectively use available insulin to burn glucose for energy. Acetone passes through the body into the urine as one of the so-called "ketone bodies."
Acetylsalicylic acid (aspirin or ASA):  Aspirin is a good example of a tradename that has entered into the language. Aspirin was once the Bayer trademark for acetylsalicylic acid.
Achalasia:  A rare disease of the esophagus (swallowing tube), usually diagnosed in adults. Abnormal function of nerves and muscles of the esophagus causes difficulty swallowing and sometimes chest pain. Regurgitation of undigested food can occur, also coughing or breathing problems related to entry of food into the lungs. The problem is weakness of the lower portion of the esophagus and failure of the lower esophageal sphincter to open.
Achilles tendonitis:  Inflammation in the tendon of the calf muscle where it attaches to the heel bone. Achilles tendonitis causes pain at the back of the leg near the heel.
Achillodynia:  Pain due to inflammation of the Achilles tendon or the bursa associated with it.
Achlorhydria:  A lack of hydrochloric acid in the digestive juices of the stomach. It can be due to many diverse causes including: pernicious anemia (an autoimmune gastritis), other autoimmune conditions - such as autoimmune thyroid disease (Hashimoto's thyroiditis) and any cause of severe chronic gastritis. Heliobacter pylori is the most common agent that may lead to destruction of parietal cells, the cells that make hydrochloric acid in the stomach, and thus lead to achlorhydria.
Achondroplasia:  The most common form of short stature with disproportionately short limbs, commonly called dwarfism. It is is caused by mutation in the fibroblast growth factor receptor-3 gene (FGFR3), which is located on chromosome 4 in chromosome band 4p16.3.
Achoo syndrome:  A disorder characterized by nearly uncontrollable sneezing provoked in a reflex fashion by the sudden exposure of a dark-adapted subject to intensely bright light, usually to brilliant sunlight. The number of sneezes is usually 2 or 3, but can be up to about 40. Often called the photic sneeze reflex or the helio-ophthalmic outburst syndrome.
Achromatopsia:  (color blindness) An hereditary disorder of sight due to a lack of cones - cells in the retina which detect color.
Acid phosphatase:  Acid phosphatase is an enzyme that works under acid conditions and is made in the liver, spleen, bone marrow and the prostate gland. High serum levels of the enzyme may indicate prostate or bone disease.
Acid reflux disease:  A condition in which acid in the stomach comes up into the esophagus. This can occur because the valve separating the contents of the stomach from the esophagus does not function properly. This is usually a function of diet, especially the persistent consumption of greasy foods.
Acid-base balance:  Acid-base balance refers to the mechanisms the body strives to keep its fluids close to neutral pH while keeping the blood slightly aklaline. Blood must be alkaline at a pH of between 7.25 and 7.65 (7.0 is neutral), even if it means making the rest of the body acid.
Acidosis:  Too much acid in the blood and body, a distinctly abnormal condition that is the result of the accumulation of acid or the depletion of alkaline reserves. One prominent example is diabetic ketoacidosis. Acidosis also occurs in lung disease, and severe kidney disease. In the extreme form acidosis is a prelude to death. Milder forms are seen with poor diet, smoking, extreme exercise, no exercise, etc. Also, unrecognized chronic infections produce acid and result in a condition of chronic subclinical acidosis which probably ages the body prematurely. Common causes are dental infections and gut wall inflammatory conditions. The opposite of acidosis is alkalosis in which there is too high a pH due to excess base or insufficient acid in the body.
Acinus, pulmonary:  The ending of a tiny airway in the lung, where the alveoli (air sacs) are located. An acinus is a round cluster of cells that looks somewhat like a knobby berry. The word "acinus" means "berry" in Latin and the plural is "acini". There are also acini, round clusters of epithelial cells, in the salivary glands and in the pancreas.
ACL:  The anterior cruciate ligament, one of the ligaments in the knee.
Acne rosacea:  This term is actually a misnomer! The appropriate term is simply rosacea which is a chronic skin disease that affects the middle third of the face with persistent redness over the areas of the face and nose that normally blush: mainly the forehead, the chin and the lower half of the nose. The tiny blood vessels in these areas enlarge (dilate) and become more visible through the skin, appearing like tiny red lines (called telangiectasias).
Acne vulgaris:  The common form of acne seen most often in teenagers or young adults, acne vulgaris is the result of overactive oil glands that become plugged, red, and inflamed.
Acoustic nerve:  the 8th cranial nerve which is concerned with hearing and the sense of balance and head position. An acoustic neuroma is a tumor on the acoustic nerve.
Acrocephalosyndactyly:  An inherited disorder causing abnormalities of the skull and face and the hands and feet. There is closure too-early of some of the sutures of the skull (craniosynostosis). This results in an abnormally shaped head, which is unusually tall and peaked, and an abnormally shaped face with shallow eye sockets and underdevelopment of the midface. There is fusion of fingers and toes (syndactyly) and broad ends of the thumbs and big toes. It is an autosomal dominant trait with boys and girls affected equally. A affected parent can have transmit the gene for the disorder or both parents can be normal with the disorder appearing in the child due to a new mutation.
Acrochordon (cutaneous papilloma or skin tag):  A small tag of skin that may have a stalk (a peduncle). An acrochordon may appear on skin anywhere although the favorite locales are the eyelids, neck, armpits (axillae), upper chest, and groin. Invariably benign, this tiny tumor of the skin usually causes no symptoms unless repeatedly irritated as, for example, by the collar. Treatment may be done by freezing with liquid nitrogen or by cutting off with a scalpel or scissors if the acrochordon is irritating or cosmetically unwanted. (acro = peak; chordon = string)
Acrocyanosis:  Blueness of the hands and feet, typically symmetrical and marked by a mottled blue or red discoloration of the skin of the fingers and wrists and the toes and ankles and by profuse sweating and coldness of the fingers and toes. It is caused by constriction of small arteries toward the end of the arms and legs.
Acrodynia:  Pain in the hands and feet. (dynia = pain)
Acromegaly:  Condition due to the production of too much growth hormone by the pituitary gland after the end of adolescence. Manifests as thickening of the skin, soft tissues, and bones of the hands and feet. These effects are insidious and slowly progressive. Ultimately they cause considerable disability (aside from the need for larger rings, gloves, and shoes) including hoarseness, sleep apnea, joint pain, cardiovascular disease, hypertension, insulin resistance, visual impairment and severe headaches. Excessive growth hormone secretion may be caused by a tumor of the pituitary or may occur in the absence of tumor. Treatment is usually possible via medication or surgery. Inadequate treatment of acromegaly is associated with increases in deaths from cardiovascular causes, cancer, and other causes. One famous person with acromegaly (and mild gigantism which is the preadult manifestation of excess growth homrone) is Tony Robbins (the motivation guru, not the actor). Click here for an image: Tony Robbins
Acrophobia:  An abnormally excessive and persistent fear of heights. Sufferers experience severe anxiety even though they usually realize that, as a rule, heights pose no real threat to them.
Actinic:  Referring to the ultraviolet (UV) rays from sunlight and UV lamps. Sunburn is an actinic burn.
Actinic keratosis:  A small rough spot on skin chronically exposed to the sun, precancerous, can develop into a skin cancer called squamous cell carcinoma, a process that typically takes years. Actinic keratoses occur most frequently in fair-skinned people. Common locations are the face, scalp, back of the neck, upper chest, forearm and back of the hand.
Active immunity:  The production of antibodies against a specific agent by the immune system. Active immunity can be acquired in two ways: by contracting an infectious disease such as chickenpox or by receiving a vaccination such as that against chickenpox. Active immunity is usually permanent. The individual is protected from the disease all his or her life.
Acupressure:  The application of pressure on specific points on the body to control symptoms such as pain or nausea. Similar in concept to acupuncture but without needles.
Acupuncture:  The practice of inserting needles into the body to reduce pain or induce anesthesia. More broadly, acupuncture is a family of procedures involving the stimulation of anatomical locations on or in the skin by a variety of techniques
Acute:  Of short duration, rapid and abbreviated in onset, in reference to a disease. ”Acute“ is a measure of the time scale of a disease and is in contrast to ”subacute“ and ”chronic.“ ”Subacute“ indicates longer duration or less rapid change. ”Chronic“ indicates indefinite duration or virtually no change.
acute abdomen:  Clinical syndrome characterized by abdominal pain of great severity associated with other symptoms and signs, usually those of acute peritonitis, which is often the result of a ruptured abdominal viscus or other abdominal catastrophe requiring urgent surgical operation.
Acute abdomen:  The abrupt (acute) onset of abdominal pain. A potential medical emergency, an acute abdomen may reflect a major problem with one of the organs in the abdomen.
Acute angle-closure glaucoma:  Increased pressure in the front chamber (anterior chamber) of the eye due to sudden (acute) blockage of the normal circulation of fluid within the eye.
Acute coronary syndromes:  A spectrum of conditions involving chest discomfort or other symptoms caused by lack of oxygen to the heart muscle (the myocardium).
Acute epiglottitis:  A very rapidly progressive infection causing inflammation of the epiglottis (the flap that covers the trachea) and tissues around the epiglottis that may lead to abrupt blockage of the upper airway and death. The inflamed epiglottis mechanically obstructs the airway; the work of breathing increases, and the retention of carbon dioxide and hypoxia (low oxygen) may result. Clearance of secretions is also impaired. These factors may result in fatal asphyxia within a few hours.
Acute fatty liver of pregnancy:  Liver failure in late pregnancy, usually from unknown cause, typically occurring in first-time pregnancies in the last trimester. If untreated, AFLP can cause complete liver failure, bleeding (because of impaired blood clotting) and death of the mother and child.
Acute HIV infection:  The body's initial reaction to infection by the HIV virus. Acute HIV infection is a flu-like syndrome that occurs immediately after a person contracts HIV (the human immunodeficiency virus 1, the agent that causes AIDS). The syndrome is characterized by fever, sore throat, headache, skin rash and swollen glands. This syndrome precedes seroconversion - the development of detectable antibodies to HIV in the blood as a result of the infection. It normally takes several weeks to several months for antibodies to the virus to develop after HIV transmission. When antibodies to HIV appear in the blood, a person will test positive in the standard ELISA test for HIV.
Acute idiopathic polyneuritis:  Also known as the Guillain-Barre syndrome, a disorder characterized by progressive symmetrical paralysis and loss of reflexes, usually beginning in the leg, with in most cases nearly complete or complete recovery. It is not associated with fever. There is paralysis involving more than one limb, most commonly the legs, and that paralysis is progressive. There is loss or diminution of reflexes, It is due to an immune response that results in the direct destruction of the myelin sheath surrounding the peripheral nerves or the axon of the nerve itself. The syndrome sometimes follow triggering events, including vaccinations. Among the vaccines reportedly associated are the swine influenza vaccine (in 1976-1977), the oral poliovirus vaccine, and tetanus toxoid. Aside from vaccinations, infection with the bacteria Campylobacter jejuni and viral infections can trigger the Guillain-Barre syndrome.
Acute leukemia:  Cancer of the white blood cells (leukemia) that characteristically comes on abruptly and (if not treated) progresses rapidly.
Acute lymphoblastic leukemia:  A form of leukemia that has a sudden onset and is characterized by the presence in the blood and bone marrow of large numbers of unusually immature white blood cells destined to become lymphocytes. These cells, called lymphoblasts, are rarely seen in the blood under normal circumstances. Treatment may include chemotherapy, radiation, biological therapy and bone-marrow transplantation. There is a high cure rate today, especially among children. Also called acute lymphocytic leukemia.
Acute membranous gingivitis:  This is trench mouth, a progressive painful infection with ulceration, swelling and sloughing off of dead tissue from the mouth and throat due to the spread of infection from the gums. Certain germs (including fusiform bacteria and spirochetes) have been thought to be involved, but the full story behind this long- known disease is still not clear.
Acute mountain sickness:  Acute mountain sickness is the effect on the body of being in a high altitude environment. It is common at high altitudes, that is above 8,000 feet (2,440 meters). Three-quarters of people have mild symptoms over 10,000 feet (3,048 meters). The occurrence depends on the altitude, the rate of ascent, and individual susceptibility. Many people experience mild AMS during the acclimatization process (the first 1 to 3 days at a given altitude). Symptoms usually start 12-24 hours after arrival at altitude and include headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep, and a general feeling of malaise. These symptoms tend to be worse at night when respiratory drive is decreased.
Acute myelogenous leukemia:  Abbreviated AML. Also called acute myeloid leukemia or acute nonlymphocytic leukemia (ANLL). A quickly progressive malignant disease in which there are too many immature blood-forming cells in the blood and bone marrow.
Acute myeloid leukemia:  A quickly progressive malignant disease in which there are too many immature blood-forming cells in the blood and bone marrow, the cells being specifically those destined to give rise to the granulocytes or monocytes, both types of white blood cells that fight infections.
Acute myocardial infarction:  An acute myocardial infarction is a heart attack. The term "myocardial infarction" focuses on the heart muscle and the changes that occur in it due to sudden deprivation of oxygen. The main change is death of heart muscle cells. The usual cause is a combination of plaque formation and ”blood slugging.“
Acute otitis media:  inflammation of the middle ear. It typically causes fluid in the middle ear accompanied by a bulging eardrum and usually pain; or a perforated eardrum, often with drainage of pus.
Acute pancreatitis:  Sudden inflammation of the pancreas (the organ - actually two organs in one anatomical structure - which makes digestive enzymes and insulin). Some people have more than one attack but recover fully after each one. The cause of acute pancreatitis is most often alcohol abuse. Other causes include use of prescribed drugs, trauma or surgery to the abdomen. In rare cases, the disease may result from infections, such as mumps. In some cases the cause is unknown.
Acute promyelocytic leukemia (APL):  A malignancy of the bone marrow in which there is a deficiency of mature blood cells in the myeloid line and an excess of immature cells called promyelocytes. APL is due to a translocation (an exchange of chromosome material) between chromosomes 15 and 17. This translocation is the cause of APL.
Acute respiratory distress syndrome (ARDS):  Respiratory failure of sudden onset due to fluid in the lungs following an abrupt increase in the permeabi
Acute thrombocytopenic purpura (ATP):  Sudden onset of low blood platelet levels with bleeding into the skin and elsewhere. ATP is due to many causes. It may, for example, constitute a potentially serious complication during the acute phase of measles.
Acute-phase proteins:  Proteins whose plasma concentrations increase (or decrease) by 25% or more during certain inflammatory disorders. The best known of acute-phase proteins is C-reactive protein (CRP), a plasma protein that rises in the blood with the inflammation from certain conditions. The level of CRP in blood plasma can rise as high as 1000-fold with inflammation. Conditions that commonly lead to marked changes in CRP include infection, trauma, surgery, burns, inflammatory conditions, and advanced cancer. Moderate changes occur after strenuous exercise, heatstroke, and childbirth. Small changes occur after psychological stress and in several psychiatric illnesses.
Ad lib:  Abbreviation for the Latin "ad libitum" meaning "at pleasure" and "at one's pleasure, as much as one desires, to the full extent of one's wishes." Used in medicine to indicate that the patient may choose his own intake of food or drink, ordinarily applied as a doctor’s order in the hospital setting.
ADA deficiency:  Lack of normal adenosine deaminase (ADA) activity, a genetic (inherited) condition causing one form of severe combined immunodeficiency (SCID) disease.
Adam's apple:  A familiar anatomic feature in the front of the neck that is due to the forward protrusion of the thyroid cartilage, the largest and most prominent cartilage of the larynx.
Adams-Stokes disease:  Sudden collapse into unconsciousness due to a disorder of heart rhythm in which there is a slow or absent pulse resulting in fainting with or without convulsions. In this condition, the normal electrical flow passing from the upper chambers of the heart to the lower chambers is interrupted. This results in a condition called a "heart block." When a heart block occurs, the heart rate usually slows considerably. This can cause inadequate blood flow to the brain and result in fainting. This condition goes by a baffling number of names including the Adams-Stokes, Morgagni, Morgagni-Adams-Stokes, Spens syndrome, and Stokes-Adams disease or syndrome.
ADD (Attention Deficit Disorder):  An inability to control behavior due to difficulty in processing neural stimuli, usually manifesting in children. While in our drug oriented society Ritalin and other drugs are used to cope with this problem, the best results are obtained when these children are taken off refined sugar.
Addison’s anemia:  A blood disorder caused by a lack of vitamin B12. Patients who have this disorder do not produce the substance in the stomach that allows the body to absorb vitamin B12. This substance is called intrinsic factor (IF). Addison’s anemia, better known today as pernicious anemia (PA), is characterized by the presence in the blood of large, immature, nucleated cells (megaloblasts) which are forerunners of red blood cells. (Red blood cells, when mature, have no nucleus). It is thus a type of megaloblastic anemia. Pernicious anemia (PA) was first described (although not by that name) in 1855 by the English physician Thomas Addison. He called it an invariably fatal ”idiopathic anemia.“ Dr. Addison also described the adrenal collapse now known as Addison’s disease.
Addison’s disease:  Long-term underfunction of the outer portion of the adrenal gland, i.e. chronic insufficiency of the adrenal cortex. This may be due to physical trauma, hemorrhage, tuberculosis of the adrenal, and destruction of the cells in the pituitary gland that secrete ACTH (adrenocorticotropic hormone) which normally drives the adrenal. Addison’s disease is characterized by bronzing of the skin, anemia, weakness, and low blood pressure. President John. F. Kennedy is said to have had Addison disease. When Addison first identified adrenal insufficiency in 1849, tuberculosis (TB) was responsible for 70-90% of cases. As the treatment for TB improved, the incidence of adrenal insufficiency due to TB of the adrenal glands greatly decreased. TB now accounts for around 20% of cases of primary adrenal insufficiency in developed countries.
Adduction:  Movement of a limb toward the midline of the body. The opposite of adduction is abduction. An adductor muscle pulls toward the midline of the body. For example, the adductor muscles of the legs pull the legs toward the midline of the body so the legs are closer together.
Adenine:  One member of the A-T (adenine-thymine) base pair in DNA. The other base pair in DNA is G-C (guanine-cytosine).
Adenocarcinoma:  A cancer that develops in the lining or inner surface of an organ. More than 95 percent of prostate cancers are adenocarcinoma.
Adenoidectomy:  The surgical removal of the adenoids.
Adenoids:  Masses of lymphoid tissue in the upper part of throat behind the nose.
Adenoma:  A benign tumor that arises in or resembles glandular tissue. If it becomes cancerous, it is called an adenocarcinoma.
Adenomyoma:  A nodule that forms around tissue of the inner uterus (endometrial tissue) as a result of adenomyosis.
Adenosine deaminase (ADA) deficiency:  An inherited condition that results in a immune deficiency disorder called severe combined immunodeficiency disease (SCIDS). Adenosine deaminase is an enzyme that plays a key role in restoring purine molecules. The first successful instance of gene therapy in humans was carried out in 1990 by Drs. W. French Anderson, R. Michael Blaese and Kenneth W. Culver who infused genetically engineered blood cells to repair ADA deficiency.
Adenosine thallium scan:  An examination of the heart to obtain information about its blood supply. Cameras take a series of pictures of the heart, then radioactive thallium is injected into the bloodstream as a tracer. The tracer attaches to certain cells and makes them visible to the camera. The tracer attaches to the muscle cells of the heart so the imaging camera can take pictures of the heart muscles. If an area of the heart does not receive an adequate flow of blood, the cells in the under-served area do not receive as much tracer and it appears as a darker area on the picture. In lieu of exercise on a treadmill, the medication adenosine is given IV to exercise the heart.
Adenosine Triphosphate (ATP):  A compound of critical importance in the storage of energy within cells in the body and in the synthesis (the making) of RNA. ATP is a nucleotide (a building block of a nucleic acid such as RNA). The body produces ATP from food. ATP stores energy which is released as the phosphates are liberated from the adenosine portion of the molecule.
Adenovirus:  A group of viruses responsible for a spectrum of respiratory disease as well as infection of the stomach and intestine, eyes, and bladder, as well as skin rash. Adenovirus respiratory diseases include a form of the common cold, pneumonia, croup, and bronchitis.
ADH (antidiuretic hormone):  A peptide molecule that is released by the pituitary gland at the base of the brain after being made nearby (in the hypothalamus). ADH has an antidiuretic action that prevents the production of dilute urine (and so is antidiuretic). A syndrome of inappropriate secretion of ADH may occur in association with oat-cell lung cancer, pancreatic cancer, prostate cancer, and Hodgkin's disease as well as a number of other disorders. ADH is also known as vasopressin.
Adhesion:  The union of two opposing tissue surfaces (often in reference to the sides of a wound). Also refers to scar tissue strands that can form in the area of a previous operation, such as within the abdomen after a laparotomy.
Adhesive capsulitis:  Constant severe limitation of the range of motion of the shoulder due to scarring around the shoulder joint. Also called a "frozen shoulder."
Adipocyte:  A fat cell, a connective tissue cell that has differentiated and become specialized in the synthesis (manufacture) and storage of fat. The adipocyte is important to the body in maintaining proper energy balance, storing calories in the form of lipids, mobilizing energy sources in response to hormonal stimulation, and commanding changes by signal secretions.
Adiponectin:  A hormone secreted by fat cells (adipocytes) that affects the body's response to insulin and may have other important effects.
Adipose:  means "fat" but is usually used to refer specifically to tissue made up of mainly fat cells such as the yellow layer of fat beneath the skin.
Adjuvant:  a method or approach which supplements another treatment. For example, adjuvant therapy for cancer after surgery can be chemotherapy or radiation. In the pharmaceutical realm an adjuvant is a substance that enhances the pharmacological effect of a drug.
Adnexa:  This Latin word (in the plural) is used in medicine in reference to appendages. For example, in gynecology the adnexa are the "appendages" of the uterus, namely the ovaries, Fallopian tubes and ligaments that hold the uterus in place.
Adrenal cortex:  The outer portion of the adrenal gland located on top of each kidney. The adrenal cortex produces steroid hormones which regulate carbohydrate and fat metabolism and mineralocorticoid hormones which regulate salt and water balance in the body. Under-function of the adrenal cortex results in Addison disease while over-function occurs in the adrenogenital syndrome and in Cushing syndrome.
Adrenal failure:  A condition in which the adrenal glands do not produce enough of the adrenal hormones that control important functions such as blood pressure.
Adrenal glands:  The adrenal glands are a pair of small glands, each of which sits on top of one of the kidneys. The adrenal is made up of an outer wall (the cortex) and an inner portion (the medulla). The adrenal glands produce hormones that help control the heart rate, blood pressure, the way the body uses food, and other vital functions. The adrenal cortex secretes steroid (cortisone-related) hormones and mineralocorticoids that regulate the levels of minerals such as sodium and potassium in the blood. The adrenal medulla makes adrenaline (epinephrine) noradrenaline (norepinephrine). Adrenaline is secreted in response to low blood levels of glucose as well as exercise and stress; it causes the breakdown of the storage product glycogen to the sugar glucose in the liver, facilitates the release of fatty acids from adipose (fat) tissue, causes dilation (widening) of the small arteries within muscle and increases the output of the heart. Noradrenaline is a neurotransmitter for the sympathetic nervous system.
Adrenal medulla:  The inner portion of adrenal gland. (The outer portion is the adrenal cortex).
Adrenaline:  A substance produced by the adrenal medulla (inside) of the adrenal gland. It is synonymous with epinephrine. Adrenaline is a sympathomimetic catecholamine, i.e. it causes quickening of the heart beat, strengthens the force of the heart contraction, opens up the bronchioles in the lungs and has numerous other effects. The secretion of adrenaline by the adrenal is part of the "fight-or-flight" reaction that we have in response to being frightened.
Adrenoleukodystrophy:  A rare genetic disorder characterized by the breakdown or loss of the myelin sheath surrounding nerve cells in the brain and progressive dysfunction of the adrenal gland. Adrenoleukodystrophy (ALD) is one of a group of genetic disorders called the leukodystrophies that cause damage to the myelin sheath of the nerve fibers in the brain. The myelin sheath is a fatty covering which acts as an electrical insulator.
Adult primary liver cancer:  A tumor in which the cancer starts during adulthood in cells in the liver. Also called hepatocellular carcinoma. Primary liver cancer is different from cancer that has metastasized (spread) from another place in the body to the liver. Hepatitis B and C appear to be the most significant causes worldwide. People who have both hepatitis B and hepatitis C may be at even higher risk if they consume more than 3 oz. (80 grams) of alcohol a day. A history of a first-degree relative with hepatocellular carcinoma also increases the risk.
Adult respiratory distress syndrome:  Respiratory failure of sudden onset due to fluid in the lungs (pulmonary edema) following an abrupt increase in the permeability of the normal barrier between the capillaries in the lungs and the air sacs. Also known as acute respiratory distress syndrome (ARDS), ARDS is the most serious response to acute lung injury. Causes include but are not limited to aspiration, inhalation of a toxic substance, widespread infection of the lungs, sepsis and near-drowning.
Adult-onset diabetes:  Non-insulin-dependent or type II diabetes, the most common form of diabetes mellitus; about 95 percent of people who have diabetes have this type. Unlike the insulin-dependent type of diabetes in which the pancreas makes insufficient insulin, people with adult-onset diabetes produce some insulin, usually excess amounts, however their cells are resistant to the action of insulin. Generally, this kind of diabetes occurs in people who are over age 40. It is strongly associated with being overweight and having indulged in a diet heavy in simple and/or refined carbs for many years. It is best treated in almost every case with certain nutritional supplements, proper diet, exercise, and weight loss. Intravenous EDTA chelation therapy has a remarkably positive effect in most cases. Most people are able to recover from this condition through these means.
Adult-onset Still disease:  Although Still disease was first described in children, it is known to begin in adults, but rarely. 100% have high intermittent fever; 100% have joint inflammation and pain, muscle pain with fevers, and develop persistent chronic arthritis. Ninety-five percent (95%) have the faint salmon-colored skin rash. Eighty-five percent (85%) have swelling of the lymph glands or enlargement of the spleen and liver; and 85% have a marked increase in the white blood cell count. Sixty percent (60%) have inflammation of the lungs (pleuritis) or the heart sack (pericarditis). Forty percent (40%) have severe anemia. And twenty percent (20%) have abdominal pain.
Advance medical directives:  These directives pertain to treatment preferences and the designation of a surrogate decision-maker in the event that a person should become unable to make medical decisions on his or her own behalf. Advance directives generally fall into three categories: living will, power of attorney and health care proxy.
Adventitia:  The outermost connective tissue covering of any organ, vessel, or other structure. For example, the connective tissue that surrounds an artery is called the adventitia because it is considered extraneous to the artery.
Adverse effect:  A harmful or abnormal result. An adverse effect may be caused by exposure to a drug or chemical. Examples of adverse effect are headache, nausea, drop in blood pressure and sudden death.
Aerobic:  Oxygen-requiring. Aerobic bacteria need oxygen to grow. Aerobic exercise requires the heart and lungs to work harder to meet the body's increased oxygen demand.
Aerobic exercise:  Brisk physical activity that requires the heart and lungs to work harder to meet the body's increased oxygen demand. Aerobic exercise promotes the circulation of oxygen through the blood. Examples of aerobic exercise include running, swimming and cycling.
Aerophagia:  The word "phage" in Greek means "to eat." Aerophagia is literally to eat air. Aerophagia is a common cause of gas in the stomach and an uncommon cause of flatulence. Everyone swallows small amounts of air when eating or drinking. However, rapid eating or drinking, chewing gum, smoking, or ill-fitting dentures may cause a significant increase in swallowed air.
Aerophobia:  An abnormal and persistent fear of flying. Sufferers experience severe anxiety even though they usually realize that the flying does not pose a threat commensurate with their fear. A second meaning is: an irrational fear of fresh air or drafts of air.
Aerosinusitis:  Sinus troubles, particularly with pain, due to changing atmospheric pressures, as when going up or down in a plane. Also called barosinusitis or sinus barotrauma.
Aerosol:  A fine mist or spray which contains minute particles.
Aerotitis:  Middle ear problems due to changing atmospheric pressures, as when a plane descends to land. The problems include ear pain, ringing, diminished hearing and, sometimes, dizziness.
Aesculapius:  The stick with the snake curled around it is the staff (the rod) of Aesculapius (also called Asklepios), the ancient god of medicine. His Greek name was Asklepios and his Roman name Aesculapius. Asklepios may have been a real person who was renowned for his gentle, humane remedies and his humane treatment of the mentally ill. His followers established temples called asclepions, temples of Asklepios, temples of healing. The greatest asklepion was in a grove of trees south of Corinth, Greece where the sick had to spend a night while the proper remedies were revealed during a dream to the priests of the temple and the cured had to make a suitable sacrifice.
Afferent:  Carrying toward. A vein is an afferent vessel since it carries blood toward from the heart. The opposite of afferent is efferent.
Afferent nerve:  A nerve that carries impulses toward the central nervous system (CNS). The opposite of an afferent nerve is an efferent nerve that carries impulses away from the CNS.
Afferent vessel:  A vessel that carries blood toward the heart. A vein or venule.
Aflatoxin:  A toxin produced by mold that is hepatotoxic (can damage the liver) and may possibly lead to liver cancer. Aflatoxins are known to cause cancer in animals. The fungi that produce aflatoxin grow on crops such as peanuts (especially) and wheat, corn, beans and rice. Aflatoxin is a problem particularly in undeveloped and developing countries. Aflatoxin is a naturally occurring mycotoxin produced by two types of mold: Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus is common and widespread in nature and is most often found when certain grains are grown under stressful conditions such as drought. The mold occurs in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration and invades all types of organic substrates whenever and wherever the conditions are favorable for its growth. Favorable conditions include high moisture content and high temperature.
African tapeworm:  The beef tapeworm (Taenia saginata), the most common of the big tapeworms that parasitizes people, contracted from infected raw or rare beef. Can grow to be 12-25 feet (3.6-7.5 m) long in the human intestine.
African tick typhus:  One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (tache noire) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.
Agammaglobulinemia:  Total or near-total absence of gamma globulin, a protein fraction of the blood rich in antibodies, due to certain genetic diseases such as Bruton agammaglobulinemia or to acquired diseases such as HIV/AIDS.
Age-related macular degeneration:  Age-related macular degeneration is a disease with its onset usually after age 60 that progressively destroys the macula, the central portion of the retina, impairing central vision. AME rarely causes blindness because only the center of vision is affected. However this can impair the ability to see straight ahead and makes it difficult to read, drive, or perform other daily activities that require fine central vision. The macula is in the center of the retina at the back of the eye. As one reads, light is focused onto the macula where millions of cells change the light into nerve signals that travel to the brain and tell it what we are seeing. This is "central vision."
Agenesis:  Lack of development of something. For example, agenesis of a toe means that toe failed to form.
Ageusia:  The inability to taste (the primary tastes are sweet, sour, bitter, and salt). Some people can taste but their ability to do so is reduced; they are said to have hypogeusia.
Aggressive angiomyxoma:  A slow-growing tumor which occurs primarily in the genital and pelvic regions. This tumor is much more common in women. It can range from relatively small tumors to football-size masses in the pelvis. Treatment consists of surgical excision. There is a relatively high rate of recurrence because the exact extent of the tumor is difficult for the surgeon to determine. These tumors appear not to have the ability to metastasize.
Agnosia:  An inability to recognize sensory inputs (sight, sound, touch). The most common agnosia is a result of brain injury damaging the rear part of the brain causing visual agnosia (inability to properly recognize what one is seeing). Tactile agnosia is the inability to recognize objects by touch alone.
Agonist:  A drug that binds to a receptor of a cell and triggers a response by the cell. An agonist often mimics the action of a naturally occurring substance. An agonist produces an action. It is the opposite of an antagonist which acts against and blocks an action. Agonists and antagonists are key agents in the chemistry of the human body and important players today in pharmacology. There are agonists now for many of the known hormones. For example, LHRH (luteinizing hormone-releasing hormone) agonists are similar to LHRH in structure and are able to mimic the effects of LHRH, a hormone that controls sex hormones in both men and women.
Agoraphobia:  An abnormal and persistent fear of public places or open areas, especially those from which escape would be difficult or help not immediately available. Persons with agoraphobia frequently also have panic disorder and characteristically become anxious if they even think about being trapped in a situation where it might be difficult to leave. People with agoraphobia also avoid the situations which bring them anxiety or panic. People with mild agoraphobia often live normal lives by avoiding anxiety-provoking situations. But, in the most severe cases, the victims may be incapacitated and be homebound. The disorder affects women twice as often as men, tends to start in the mid to late 20’s and the onset may appear triggered by a traumatic event. Agoraphobia comes from the Greek agora, marketplace + phobos, fear = fear of the marketplace.
Agranulocytosis:  A marked decrease in the number of granulocytes. Granulocytes are a type of white blood cell filled with microscopic granules that are little sacs containing enzymes that digest microorganisms. Granulocytes are part of the innate, somewhat non specific infection-fighting immune system. They do not respond exclusively to specific antigens, as do B-cells and T-cells. Agranulocytosis results in a syndrome of frequent chronic bacterial infections of the skin, lungs, throat, etc. Although "agranulocytosis" literally means no granulocytes, there may, in fact, be some granulocytes but too few of them, i.e. granulocytopenia. Agranulocytosis can be genetic and inherited or it can be acquired as, for example, an aspect of leukemia. Neutrophils, eosinophils and basophils are all types of granulocytes.
Agranulocytosis, infantile genetic:  Children born with this condition lack neutrophils (a type of white blood cell that is important in fighting infection). These children suffer frequent infections from bacteria which in the past led to death in three-quarters of cases before 3 years of age.
Ague:  A fever marked by paroxysms of chills, fever, and sweating recurring regular intervals. Also a fit of shivering, a chill. Hence, ague can refer to both chills and fevers.
Agyrophobia:  Abnormal and persistent fear of crossing streets, highways and other thoroughfares; fear of thoroughfares themselves. Sufferers experience anxiety even though they realize that streets, highways and other thoroughfares pose no threat commensurate with their fear. Formed from the Greek gyrus (turning or whirling) and the Greek phobos (fear). The first letter, "a," is privative--that is, it creates a negative. Thus, an agyrophobiac shuns or avoids the whirl of traffic.
AID (artificial insemination by donor):  A procedure in which a fine catheter (tube) is inserted through the cervix (the natural opening of the uterus) into the uterus (the womb) to deposit a sperm sample from a donor other than the woman's mate directly into the uterus. The purpose of this procedure is to achieve fertilization and pregnancy. AID is also called heterologous insemination. AID is distinguished from homologous insemination, that is artificial insemination by husband (AIH) (see below).
AIDS (Acquired Immunodeficiency Syndrome):  It is a multifactoral collapse of the immune system strongly associated with the human immunodeficiency virus (HIV) but requiring other debilitating factors to be present for clinical expression.
AIDS dementia complex:  The AIDS dementia complex is a brain disorder that occurs in people with AIDS that causes the loss of cognitive capacity, affecting the ability to function in a social or occupational setting. The exact mechanism by which it is triggered has not been determined.
AIDS-Related Complex:  In the early years of the AIDS epidemic, this term was used to describe people with HIV infection who had mild symptoms of illness, such as swollen lymph glands. It is rarely used today.
AIH (artificial insemination by husband):  A procedure in which a fine catheter (tube) is inserted through the cervix (the natural opening of the uterus) into the uterus (the womb) to deposit a sperm sample from the woman's mate directly into the uterus. The purpose of this procedure is to achieve fertilization and pregnancy. AIH is distinguished from artificial insemination by donor (AID) in which the donor is a man other than the woman's mate (see above). AIH is also known as homologous insemination.
Ailurophobia:  An abnormal and persistent fear of cats which produces an undue anxiety reaction even though sufferers realize their fear is irrational. Sufferers of ailurophobia may fear not only the scratch or bite of a cat, but also the "evil mystique" of cats.
Air-conditioner lung:  A form of the sick building syndrome caused by organisms that contaminate humidifiers and the piping of air conditioner ducts. The air conditioner blows cold air containing spores of the organisms throughout the building. The organisms responsible for air-conditioner lung are the same as cause farmer's lung which is due to repeated inhalation of dust from hay. (The organisms are thermophilic actinomycetes).
Airway:  The path air follows to get into and out of the lungs. The mouth and nose are the normal entry and exit ports. Entering air then passes through the back of the throat (pharynx), continues through the voice box (larynx), down the trachea, and finally out the branching tubes known as bronchi.
Airway obstruction:  Partial or complete blockage of the breathing tubes to the lungs. Obstruction of the airway can be due to different causes including foreign bodies, allergic reactions, infections, anatomical abnormalities and trauma
Akinesia:  Impaired body movement; without movement, or without much movement. Akinesia is a term used in neurology to denote the absence or poverty of movement.
Akinetic:  Without movement (or without much movement). A term used in neurology to denote the absence or poverty of movement.
Akinetic mutism:  A state in which a person is mute and unmoving akinetic. A person with akinetic mutism has sleep-waking cycles but, when apparently awake, with eyes open, lies mute, immobile and unresponsive. It is often due to damage to the frontal lobes of the brain.
Akinotopsia:  Akinetopsia is caused by a lesion in area V5 of the extrastriate cortex. It can also be caused as a side effect of certain antidepressant drugs, or due to damage by a stroke or certain brain surgeries. Akinetopsia is a rare neuropsychological disorder, a disorder between the nervous system and mental functions, in this case between the brain and motion perception. In this disorder the person affected by it cannot perceive motion. Imagine the effects of a strobe light and how you do not seem to detect motion, but rather see a series of still images. However, there is more to akinetopsia than perceiving a series of changing static images without motion. Recall pictures of city lights taken while in a moving car at night. The lights have a comet-like trail behind them. For people with this disorder, the comet trail of images is present as well. The movement of an arm can appear as several, fuzzy arms trailing after the original one. Only when objects come to a stand-still is the world around them seen normally. However, when things are moving there is a trail of repetitive images, such as one dog appearing several times in a trail after itself which then catch up to the original image when that object is standing still. In some cases akinetopsia can be treated by brain surgery or discontinuation of antidepressants.
Alanine:  An amino acid, one of the 20 amino acids that serve as the building blocks in protein. Alanine is not an "essential" amino acid. (It is not essential to the diet, but can be made by the body from other substances. Alanine was discovered in protein in 1875.
Alanine aminotransferase (ALT):  An enzyme that is normally present in liver and heart cells. ALT is released into blood when one or both of these organs are damaged. Blood ALT levels are thus elevated with liver damage (for example, from viral hepatitis) or with an insult to the heart (for example, from a heart attack). Some medications can also raise ALT levels. ALT is also called serum glutamic pyruvic transaminase (SGPT).
Albinism:  Partial or total lack of the pigment melanin in the skin, hair and iris. The term "albino" was first applied by the Portuguese to "white" people they encountered in West Africa. Those "white" people probably had partial or complete albinism, an inherited lack of pigment in the skin, hair, and eyes. The lack of pigment in the eye impairs vision and often leads to jerky involuntary rhythmic eye movements called nystagmus.
Albright syndrome:  A genetic disorder of bones, skin pigmentation and hormonal problems with premature sexual development. Also called McCune-Albright syndrome and polyostotic fibrous dysplasia.
Albuginea:  Tough white fibrous tissue. The tunica albuginea of the testis, for example, is the layer of dense whitish inelastic tissue that surrounds the testes.
Albumen:  The white of an egg.
Albumin:  The main protein in human blood and the key to the regulation of the osmotic pressure of blood. Chemically, albumin is soluble in water, precipitated by acid, and coagulated by heat.
Albuminuria:  More than the normal amount of albumin in the urine. Albumin is the main protein in human blood and it is the key to the regulation of the osmotic pressure of blood. Some albumin is normal in the urine. But too much albumin in the urine means that protein is leaking through the kidney, most often through the glomeruli. Albuminuria can mean many things. Thus, for example, albuminuria may be a sign of significant kidney disease or it may simply be a sequel of vigorous exercise. Albuminuria is a form of proteinuria.
Alcohol:  An organic chemical in which one or more hydroxyl (OH) groups are attached to carbon (C) atoms in place of hydrogen (H) atoms. Common alcohols include ethyl alcohol or ethanol (found in alcoholic beverages), methyl alcohol or methanol (can cause blindness) and propyl alcohol or propanol (used as a solvent and antiseptic). Rubbing alcohol is a mixture of acetone, methyl isobutyl ketone, and ethyl alcohol. In everyday talk, ”alcohol“ usually refers to ethanol as, for example, in wine, beer, and liquor. It can cause changes in behavior and be addictive. The word "alcohol" came from the Arabic "al" (the) = "kuhl" (a fine impalpable powder) and referred originally to finely powdered antimony which women used to tint their eyelids.
Aldose reductase inhibitor:  A class of drugs used to prevent eye and nerve damage in diabetes. Aldose reductase is an enzyme that is normally present in the eye and in many other parts of the body. It helps change glucose into a sugar alcohol called sorbitol. Too much sorbitol trapped in eye and nerve cells can damage these cells, leading to retinopathy (retinal disease) and neuropathy (nerve disease). Drugs that prevent or slow the action of aldose reductase may represent a means to prevent or delay these complications of diabetes.
Aldosterone:  A hormone made by the outer portion (cortex) of the adrenal gland that regulates the balance of salt and water in the body. It is secreted in response to low salt levels and activates the MR (for mineralocorticoid receptor) gene. The product of the MR gene stimulates the kidney to reabsorb and retain salt, thereby retaining water. (An MR gene mutation leads to salt retention and high blood pressure early in life which becomes much worse with pregnancy.)
Aldosteronism:  Overproduction of the hormone aldosterone from the cortex (the outer layer) of the adrenal gland or a tumor containing that type of tissue. Excess aldosterone results in low potassium levels (hypokalemia), underacidity of the body (alkalosis), muscle weakness, excess thirst (polydipsia), excess urination (polyuria), and high blood pressure (hypertension). Also called hyperaldosteronism or Conn’s syndrome.
Alembic:  A type of still, an apparatus used in the process of distillation. Alembics were employed in chemistry and biomedical laboratories as well as in distilling cognac. By extension, "alembic" is anything that refines or transmutes as if by distillation. For example, the alembic of the author's mind.
Alexia:  A loss of the reading ability or the ability to understand the written word due to brain damage that disconnects these functions. Alexia is a complex visual disturbance resulting from disease or damage in the visual-association areas at the back of the brain. (G. literally without word)
Algophobia:  An abnormal and persistent fear of pain which is excessive, beyond that which is expected under the circumstances, producing an anxiety reaction. (G. pain fear)
Alien hand syndrome:  The feeling that one's hand is possessed by a force outside of ones control. The syndrome typically arises after trauma to the brain, after brain surgery or after a stroke or an infection of the brain. A person with the alien hand syndrome can feel sensation in the affected hand but thinks that the hand is not part of his or her body and believes there is no personal control over its movement, that it belongs to an alien. There is no cure for alien hand. All a patient can do to control the problem is to keep the hand busy by having it hold an object.
Alkaline phosphatase:  An enzyme made in the liver, bone, and the placenta and normally present in high concentrations in growing bone and in bile. It is released into the blood during injury and during normal activities such as bone growth and pregnancy. It is measured in a routine blood test. Abnormally high blood levels of alkaline phosphatase may indicate disease in bone or liver, bile duct obstruction, or certain malignancies. The enzyme is often elevated in chronic myelogenous leukemia. Abnormally low levels of alkaline phosphatase is a genetic condition called hypophosphatasia which results in bone deformities.
Alkalosis:  A dangerous decrease in the normal acidity of the blood where there is too much base in the blood and body resulting from accumulation of base or the depletion of acid. The pH of the alkalotic body measures above normal. It can be caused by high altitudes, hyperventilation, and excessive vomiting. The opposite of alkalosis is acidosis in which there is too low a pH due to excess acid or insufficient base in the body.
Alkaptonuria:  A genetic metabolic disorder due to deficiency of the enzyme homogentisic acid (HGA) dioxygenase. Deficiency of this enzyme leads to the three cardinal features of alkaptonuria --the presence of homogentisic acid in the urine, ochronosis (bluish-black pigmentation in connective tissue), and arthritis. The presence of HGA in the urine causes it to turn black upon standing when exposed to air.
ALL:  Acute lymphoblastic leukemia, also called acute lymphocytic leukemia, an acute rapidly progressive form of leukemia characterized by the presence in the blood and bone marrow of large numbers of unusually young (immature) white blood cells destined to become lymphocytes. These cells, called lymphoblasts, are rare items in the blood under normal circumstances.
Allele:  An alternative form of a gene. One of the different forms of a gene that can exist at a single locus (spot on a chromosome). Also one of the different forms of any segment of a chromosome.
Allergen:  A substance that is foreign to the body and can cause an allergic reaction in a susceptible person. Examples are pollen, house dust, cat danders, and perfumes.
Allergic conjunctivitis:  Inflammation of the whites of the eyes (the conjunctivae) with itching and redness of the eyes and tearing, due to allergy.
Allergic contact dermatitis:  A red, itchy, weeping reaction where the skin has come into contact with an allergen; for example poison ivy, poison oak or poison sumac or certain preservatives in creams and lotions. This type of reaction reflects a specific sensitivity or allergy to a specific substance. Also called allergic contact eczema.
Allergic granulomatosis (or allergic granulomatous angiitis):  A disease (also often called the Churg-Straus syndrome) characterized by inflammation of the blood vessels in persons with a history of asthma or allergy.
Allergic rhinitis:  Medical term for ”hay fever,“ a condition due to allergy that mimics a chronic cold. ”Hay fever“ is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances can cause the allergic symptoms in hay fever, most commonly pollen and most commonly in the Springtime. (Rhinitis means "irritation of the nose" and is derivatived from Rhino, referring to the nose). Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. Post-nasal dripping of clear mucus frequently provokes coughing. Eye itching, redness, and tearing frequently accompany the nasal symptoms. If this condition persists throughout the year it is termed perennial allergic rhinitis. If not it is called seasonal allergic rhinitis.
Allergy:  A mistaken reaction to foreign substances by the immune system. Mistaken in that these foreign substances are usually harmless. The substances that trigger allergy are called allergens. Examples include pollens, dust mite, molds, danders, and certain foods. People with allergies are said to be allergic or atopic. Allergens cause the over-production of immunoglobulin E (IgE), an antibody we all have in small amounts which is designed to protect us from parasites. During the sensitization period in allergy, IgE is overproduced. It coats mast cells which contain histamine. Histamine causes inflammation and the typical allergic symptoms when released in the presence of allergens.
Allergy desensitization (or allergy immunotherapy):  Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic, in order to reduce the strength of the IgE and its effect on the mast cells; very effective for allergies to pollen, mites, cats, and especially stinging insects. Usually takes 6 months to a year to become effective and injections are usually required for 3-5 years.
Allergy scratch test:  Test done on the skin to identify the allergen that triggers an allergic reaction.
Allergy to cockroaches:  A condition that manifests as an allergic reaction when one is exposed to tiny particles from cockroaches. Asthma can be due to exposure to cockroach allergens (allergy-provoking substances). These substances are the proteins shed or excreted by the cockroaches.
Allergy to cow’s milk:  Casein and whey are the two major proteins of human milk and most milk-based formulas. Some (less than 8% of) infants have a true allergy to the cow proteins that are in milk-based formulas.
Alloerotic:  Having to do with sexual excitement toward the same sex. The opposite is heteroerotic.
Allopathy:  The system of medical practice which treats disease by the use of remedies which produce effects different from those produced by the disease under treatment. ”Mainstream medicine“ is allopathic in nature. The term "allopathy" was coined in 1842 by C.F.S. Hahnemann to designate the usual practice of medicine as opposed to homeopathy, the system of therapy he founded based on the concept that disease can be treated with drugs (in minute doses) thought capable of producing the same symptoms in healthy people as the disease itself.
Alopecia:  Baldness. There are many types of alopecia, each with a different cause. Alopecia may be localized to the front and top of the head as in common male pattern baldness. It may be patchy as in a condition called alopecia areata. Or it can involve the entire head as in alopecia capitis totalis. The word "alopecia" comes from the Greek "alopex" for "fox." Foxes are less furry when afflicted with a skin disease (the "mange") which causes them to lose their hair.
Alopecia areata:  Patchy baldness (alopecia means baldness and areata means occurring in patches) which typically begins on the scalp and sometimes progresses to complete baldness and even loss of body hair. The hair loss tends to be rather rapid and asymmetrical. It affects both males and females. It tends to occur most often in children and young adults. The most common pattern of alopecia areata is one or more spots of hair loss on the scalp. There is also a form of more generalized thinning. The cause appears to involve an autoimmune mechanism. Biopsies of affected skin show lymphocytes inside of hair follicles where lymphocytes normally are not present. The cause is unknown.
Alopecia capitis totalis:  Loss of all of the scalp hair with normal hair elsewhere on the body.
Alopecia traumatica:  Loss of hair caused by grooming methods that attempt to straighten the natural kinkiness of hair in order to make the hair more manageable. It is a result of stress traction injury from tight rollers and braiding as well as overheating the hair shafts. Vigorous combing and chemical bleaches and styling products can additionally irritate the scalp to cause further hair loss.
Alopecia universalis:  Absence of all of the hair, not only on the scalp, but also on the entire body. Affected individuals are born without eyebrows and eyelashes and never develop axillary or pubic hair. They have hair follicles which are devoid of hair. The disorder is inherited as an autosomal recessive trait. It is caused by a mutation in a gene dubbed HR in chromosome band 8p21.2 that is the human homolog of the mouse "hairless" gene - the human version of the gene in the mouse that is responsible for hairless mice.
Alpha cell, pancreatic:  A type of cell in the pancreas. Within the pancreas, the alpha cells are located in areas called the islets of Langerhans. Alpha cells make and release glucagon which raises the level of glucose (sugar) in the blood. Alongside are the beta cells which make insulin.
Alpha Fetoprotein (AFP):  Alpha Fetoprotein (AFP): A plasma protein normally produced by the fetus. It serves as the basis for tests. AFP is manufactured mainly in the fetus's liver and, also, in the fetal gastrointestinal tract and the yolk sac, a structure temporarily present during embryonic development. The level of AFP is typically high in fetal blood. It goes down in the baby's blood after birth. And by a year of age, it is virtually undetectable. During pregnancy, AFP crosses the placenta from the fetal circulation and appears in the mother's blood. The level of AFP in the mother's blood (the maternal serum AFP) provides a screening test for a number of disorders including:
  • Open neural tube defects (anencephaly and spina bifida)
  • Down syndrome (and other chromosome abnormalities)

The maternal serum AFP (MSAFP) tends to be:

  • High with open neural tube defects such as anencephaly and spina bifida (meningomyelocele)
  • Low with Down syndrome (trisomy 21, an extra chromosome number 21).

AFP production is essentially nil after a year of age. However, it starts up again under the stimulus of some diseases in the liver. It may be produced by the liver in viral hepatitis and cirrhosis of the liver. AFP is also made by primary liver tumors (hepatomas) and by germ cell tumors (teratocarcinoma and embryonal cell carcinomas). A person's serum AFP level can therefore be used to help detect these conditions and monitor their treatment.

Alpha interferon:  The interferons are specialized proteins (lymphokines) produced by the body in response to an infection. these substances interfere with cell infection. There are 3 main classes of interferon, alpha, beta, and gamma.
Alpha thalassemia:  A blood disorder, thalassemia is not one disease but rather a group of disorders that have a single feature in common: they all have a genetic defect in the production of hemoglobin, and thus produce a form of anemia. The problem in the thalassemias is with globin production. The thalassemias are classified according to the type of globin polypeptide chain that is underproduced. The alpha chain is involved in alpha thalassemia (and the beta chain is affected in the more familiar beta thalassemia).
Alpha-1 Antitrypsin Deficiency:  Also know as Also called: AATD, Alpha-1, inherited emphysema, Alpha-1 antitrypsin deficiency is an inherited disorder that can cause lung disease in adults and liver disease in adults and children. Alpha-1 antitrypsin (AAT) is a protein that protects the lungs. The liver makes the protein, and releases it into the bloodstream. Because of a genentic abnormality, some people have little or none of it. Not having enough AAT puts you at risk of emphysema or liver problems. Three in four adults with a severe deficiency will get emphysema, some when they are younger than 40. Smoking increases risk. Children with AAT deficiency can develop liver problems that persists for life. AAT deficiency can be treated but not cured. One treatment involves adding to or replacing the missing protein. A lung transplant may be an option if the patient is seriously ill. Staying away from cigarette smoke is crucial. A blood test can diagnose the deficiency. If present relatives should be tested.
Alpha-Fetoprotein (AFP):  AFP is a plasma protein that is normally produced by the fetus. It serves as the basis for some valuable tests. AFP is manufactured principally in the fetus's liver and, also, in the fetal gastrointestinal tract and the yolk sac, a structure temporarily present during embryonic development. The level of AFP is typically high in the fetus's blood. It goes down in the baby's blood after birth. And by a year of age, it is virtually undetectable. During pregnancy, AFP crosses the placenta from the fetal circulation and appears in the mother's blood. The level of AFP in the mother's blood (the maternal serum AFP) provides a screening test for a number of disorders including open neural tube defects (anencephaly and spina bifida); and Down syndrome and other chromosome abnormalities. The maternal serum AFP (MSAFP) tends to be high with open neural tube defects such as anencephaly and spina bifida (meningomyelocele); and low with Down syndrome (trisomy 21, an extra chromosome number 21). AFP production is essentially nil after a year of age. However, it starts up again under the stimulus of some diseases in the liver. It may, for example, be produced by the liver in viral hepatitis and cirrhosis of the liver. AFP is also made by primary liver tumors (hepatomas) and by germ cell tumors (teratocarcinoma and embryonal cell carcinomas). A person's serum AFP level can therefore be used to help detect these conditions and monitor their treatment.
ALS (Amyotrophic Lateral Sclerosis):  A classic motor neuron disease. Motor neuron diseases are progressive chronic diseases of the nerves that come from the spinal cord responsible for supplying electrical stimulation to the muscles. ALS is also known as Lou Gehrig's Disease in North America after the baseball player who had it. Gehrig was born in 1903, and he died in 1941 at the age of 38. ALS strikes in mid-life, most often in the fifth through seventh decades of life. Men are about one-and-a-half times more likely to have the disease as women. It affects about 20,000 Americans at any one time with 5,000 new cases occurring in the United States each year. ALS occurs when specific nerve cells in the brain and spinal cord that control voluntary movement gradually degenerate. The loss of these motor neurons causes the muscles under their control to weaken and waste away, leading to paralysis. The cause of this disease process is still unknown. ALS manifests itself in different ways, depending on which muscles weaken first. Symptoms may include tripping and falling, loss of motor control in hands and arms, difficulty speaking, swallowing and/or breathing, persistent fatigue, and twitching and cramping. ALS is usually progressive and fatal. The usual causes of death of patients with motor neuron diseases are not directly related to the disease, but result from simultaneous additional illnesses, often infections. ALS usually leads to death within 5 years of the time the diagnosis of ALS is made; the range is from 2 to 7 years.
ALT (alanine aminotransferase):  An enzyme normally present in liver and heart cells that is released into the bloodstream when the liver or heart is damaged from, for example, viral hepatitis or a heart attack). Some medications can also raise ALT levels. ALT is also called serum glutamic pyruvic transaminase (SGPT).
Alternative splicing:  Different ways of combining the DNA of a gene so as to create different variants of the protein product of that gene. Alternative splicing is a regulatory mechanism by which variations in the incorporation of a gene's exons, or coding regions, into messenger RNA lead to the production of more than one related protein, or isoform.
Altitude illness:  Altitude illness (or altitude sickness) is a disorder caused by being at high altitude. It commonly occurs above 8,000 feet. The cause of altitude illness is a matter of oxygen pressure. At 12,000 feet there are roughly 40% fewer oxygen molecules per breath. In order to oxygenate the body effectively, breathing rate must increase. This extra ventilation increases the oxygen content in the blood, but not to sea level concentrations. Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen. In addition, high altitude and lower air pressure cause fluid to leak from the capillaries which can cause fluid build-up in both the lungs and the brain. Continuing to higher altitudes without proper acclimatization can lead to potentially serious, even life-threatening illnesses.

Altitude, acclimatization to: Adjustment to changes in altitude. The main cause of altitude sickness is going too high too fast. Given time, the body can adapt to the decrease in oxygen concentration at a specific altitude, process known as acclimatization. To acclimatize, a number of changes take place in the body occur to allow it to operate with decreased oxygen: the depth of respiration increases; the pressure in the pulmonary arteries increases forcing blood into portions of the lung which are normally not used at sea level; more red blood cells are made; more 2,4-DPG is made which facilitates the release of oxygen from hemoglobin to the body tissues. Acclimatization generally takes 1 to 3 days at a given altitude. Altitude is defined on the following scale:

High altitude: 8,000 - 12,000 feet (2,438 - 3,658 meters);
Very high altitude: 12,000 - 18,000 feet (3,658 - 5,487 meters); and
Extremely high altitude: 18,000+ feet (5,500+ meters).

Most people can go up to 8,000 feet (2,438 meters) with minimal effects. If you have been at that altitude before and had no problems, you can probably return to that altitude without problems if (and only if) you are properly acclimatized..If you have not been to high altitude before, caution is strongly recommended. No specific factors such as age, sex, or physical condition are known to correlate with the susceptibility to altitude sickness. Some people are simply more susceptible than others. There is no telling, so caution is the better part of wisdom..

Alutomania:  A morbid preoccupation with thoughts about cleanliness, exhibited by obsessive washing.
Alveolar hydatid disease (AHD):  A parasitic disease caused by the larval stage of a microscopic tapeworm Echinococcus multilocularis.
Alveoli:  Tiny air sacs located at the very ends of the bronchioles within the lungs. A single sac is called an alveolus. The exchange of oxygen and carbon dioxide takes place in the alveoli.
Alzheimer disease:  A progressive degenerative disease of the brain that leads to dementia. On a cellular level, Alzheimer disease is characterized by unusual helical protein filaments in nerve cells (neurons) of the brain. These odd twisted filaments are called neurofibrillary tangles. On a functional level, there is degeneration of the cortical regions, especially the frontal and temporal lobes, of the brain. About four million Americans suffer from it, including U.S. President Ronald Reagan. The German psychiatrist and pathologist Alois Alzheimer (1864-1915) first described this form of presenile dementia in 1907.
Amalgam:  In dentistry, an alloy of mercury, silver, tin, etc. used in dental restorations. In susciptible people mercury has proven to provoke degeneration of the immune system, digestive functions, fatigue, and brain fog.
Amastia:  A rare condition wherein the normal growth of the breast or nipple does not occur. Unilateral amastia just on one side is associated with absence of the pectoral muscles. Bilateral amastia is associated in 40% of cases with multiple congenital anomalies involving other parts of the body as well. Amastia is distinguished from amazia (see below)
Amathophobia:  An abnormal and persistent fear of dust. Sufferers experience anxiety even though they realize dust poses no threat. From the Greek "amathos" (sand) and "phobos" (fear).
Amaurosis fugax:  A symptom described as a shade coming down over the eye. A partial or complete loss of sight that is temporary usually related to atherosclerosis in the blood vessels that supply the brain. It can also occur with excessive acceleration, as in flight. Amaurosis is the Greek word for darkening, dark, or obscure. The ancients used it to refer to dimmed vision, especially if there was nothing they could see that was wrong with the eye itself. Fugax is related to fugitive (fleeing). Amaurosis fugax therefore means a fleeting loss of vision.
Amazia:  A condition wherein the breast tissue is absent but the nipple is present. Amazia typically is a result of radiation or surgery.
Amblyopia:  Impaired vision due to lack of use of an eye when the brain favors the other eye. The most common causes of amblyopia are strabismus and anisometropia. In strabismus, the eyes are not aligned. The brain favors one eye over the other and the ignored eye is not adequately stimulated and the visual brain cells do not mature normally. Anisometropia occurs when the eyes have an unequal refractive power. One eye is myopic (nearsighted) and the other hyperopic (farsighted). Because the brain cannot reconcile this difference, it develops a preference for the image coming from one eye only.
Ambulance:  The ambulance began as a walking hospital,"un hôpital ambulant" in French, meaning literally "a walking hospital." The "hôpital ambulant" was devised during the campaigns of Napoleon to bring medical aid directly to troops in the field. The original "hôpital ambulant" was a mobile unit designed to carry dressings and drugs to the wounded and evacuate the injured from the line of battle. The British came up with their own version of the "hôpital ambulant" dropped the "hôpital" and corrupted "ambulant" to "ambulance." The French then rejected their own "hôpital ambulant" and embraced the English "ambulance." So, in France today you can no longer see a hospital walking but "ambulances" are very much in evidence.
Ambulant:  Means the same as "ambulatory," able to ambulate, i.e. walk about.
Ambulatory:  Able to ambulate, to walk about, not bed-ridden or hospitalized.
Ambulatory care:  Medical care provided on an outpatient basis. Ambulatory care is given to persons who are not confined to a hospital but rather are "ambulatory," able to ambulate or walk about.
AMC (arthrogryposis multiplex congenita):  a disorder that develops before birth is evident at birth and involves limited mobility of many (multiple) joints. The range of motion of the joints in the arms and legs is usually limited or fixed. The impairment of joint mobility in AMC is often accompanied by overgrowth of fibrous tissue in the joints with further immobilization of the joints (fibrous ankylosis). The mechanisms responsible for AMC are thought to include: neurologic deficits, muscle defects, connective tissue and skeletal defects, fetal crowding or fetal constraint, and maternal neuromuscular diseases. Arthrogryposis means crooking of the joint. It comes from the Greek "arthro-", joint + "gryposis", crooking. Arthrogryposis multiplex congenita can be translated (very roughly) as "lots of crooked joints at birth."
Ameba (also amoeba):  . A single-celled (protozoan) organism that constantly changes shape. The word ”ameba“ is from the Greek ”amoibe“ meaning ”change.“ Ameba can infect the bowels to cause diarrhea and the liver to cause abscess formation. This illness is called amoebiasis.
Amebic colitis:  Amebic dysentery involves inflammation of the intestine with ulcers in the colon due to infection with an ameba (Entamoeba histolytica), a single-celled parasite transmitted to humans via contaminated water and food. E. histolytica has the ability to penetrate the gut wall and cause abscesses in the liver - often a fatal event. Entamoeba. coli is a more subtle parasite which does not penetrate the gut wall. It is not a fulminating disease and thus often goes undiagnosed. It is a common parasite in the United States infecting many unsuspecting people.
Amebic dysentery:  inflammation of the intestine with ulcers in the colon due to infection with an ameba (Entamoeba histolytica). This single-celled parasite is transmitted to humans via contaminated water and food.
Amenorrhea:  Absence or cessation of menstruation, divided into primary and secondary amenorrhea. Primary amenorrhea is where menstruation never takes place. It fails to occur at puberty. In secondary amenorrhea menstruation starts but then stops. The absence of menstruation during pregnancy and lactation is a form of physiologic secondary amenorrhea. The word "amenorrhea" is compounded from three Greek roots "a-", no + "men", month + "rhoia", flow = no monthly flow. Amenorrhea is less commonly called amenia.
Amine:  A chemical compound containing nitrogen derived from ammonia. (The name "amine" was derived from the word "ammonia.")
Amino acids:  The 20 building blocks of protein. The sequence of amino acids in a protein and, hence, the function of that protein are determined by the genetic code in the DNA. The 20 amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.
Amino acids:  molecules that (in technical terms) contain a basic amino (-NH2) group, an acidic carboxyl (-COOH) group and a side chain attached to an end carbon atom. The 20 essential amino acids (not made by the body and thus required to be present in the diet) are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.
AML (acute myeloid leukemia):  (also known as acute myelogenous leukemia), a quickly progressive malignant disease in which there are too many immature blood-forming cells in the blood and bone marrow, the cells being specifically those destined to give rise to the granulocytes or monocytes, both types of white blood cells that fight infections. In AML, these cells do not mature and so become too numerous. AML can occur in adults or children. Acute myeloid leukemia is also known as acute nonlymphocytic leukemia (ANLL).
Amnesia:  An impairment or lack of memory. Amnesia after a trauma event can be either antegrade (lack of memory related to events occurring after the event) or retrograde (lack of memory related to events occurring before the event).
Amnesia, antegrade:  Amnesia in which the lack of memory relates to events occurring after a traumatic occurrence.
Amnesia, retrograde:  Amnesia in which the lack of memory relates to events occurring before a traumatic occurrence.
Amniocentesis:  Procedure used in prenatal diagnosis to obtain amniotic fluid which can be used for genetic and other diagnostic tests.
Amnion:  A thin membrane surrounding the fetus during pregnancy. The amnion is the inner of the two fetal membranes (the chorion is the outer). It contains the amniotic fluid.
Amniotic fluid:  The fluid bathing the fetus and serving as a shock absorber.
Amoeba:  Also ameba. A single-celled (protozoan) organism that constantly changes shape. The word ”ameba“ is from the Greek ”amoibe“ meaning ”change.“ Ameba can infect the bowels to cause diarrhea and the liver to cause abscess formation.
Amphetamine:  A drug with a stimulant effect on the central nervous system that can be both physically and psychologically addictive when overused. This drug has been much abused recreationally. The street term "speed" refers to stimulant drugs such as amphetamine.
Amplification of DNA:  The production of multiple copies of a gene or of any sequence of DNA. Gene amplification plays a role in cancer cells.
Ampulla:  a dilated (widened) segment in a tubular structure.
Ampulla of Vater:  A small muscle located at the junction where of the common bile duct (from the liver and pancreas) empties into the duodenum (the upper part of the small intestine). Bile from the liver and secretions from the pancreas come through the ampulla of Vater to mix with food in the duodenum for digestion.
Ampullary carcinoma:  Cancer of the ampulla of Vater (see above). Because of its location, this cancer can cause obstruction of the common bile duct and prevent bile from flowing into the intestine and out of the body. The chemicals usually eliminated from the body in bile — in particular, bilirubin (a breakdown product of hemoglobin) — accumulate in the blood and cause jaundice (yellow skin and eyes) and itching. The stool becomes light-colored and the urine dark-colored since the accumulating bilirubin (which is yellow to dark brown) is eliminated in the urine instead of the stool.
Amputation:  Removal of part or all of a body part enclosed by skin, for example, removal of part of a finger or an entire finger would be termed an amputation. Removal of an appendix would not be termed amputation. A person who has undergone an amputation is called an amputee.
AMS (acute mountain sickness):  Acute mountain sickness (AMS) is the effect on the body of being in a high altitude environment. AMS is common at high altitudes, that is above 8,000 feet (2,440 meters). Three-quarters of people have mild symptoms of AMS over 10,000 feet (3,048 meters). The occurrence of AMS depends on the altitude, the rate of ascent, and individual susceptibility.
AMS (atypical measles syndrome):  An altered expression of measles, AMS begins suddenly with high fever, headache, cough, and abdominal pain. The rash may appear 1 to 2 days later, often beginning on the limbs. Swelling (edema) of the hands and feet may occur. Pneumonia is common and may persist for 3 months or more. AMS occurs in persons who were incompletely immunized against measle.
Amusia:  Amusia refers to a family of disorders which are united by the inability to recognize musical tones or rhythms and/or the inability to reproduce them. Amusia can be congenital or acquired sometime later in life as from, for example, brain damage. The term "amusia" is composed of a- + -musia which means the lack of music. Recent research suggests the human brain has neural networks specifically for processing music. Amusia is, at the most basic level, thought to be a deficiency in fine-grained perception of pitch.
Amylase:  An enzyme produced in the pancreas and salivary glands that helps in the digestion of starches. Elevation of blood amylase is common in pancreatitis.
Amyloidosis:  A disorder that results from the abnormal accumulation of a protein called amyloid, in various tissues of the body. Amyloid can be deposited in a localized area, and not be harmful, or in can cause serious changes in virtually any organ of the body. Amyloidosis can occur as an isolated disease or as a result another illnesses such as multiple myeloma, chronic infections, or chronic inflammatory diseases (such as rheumatoid arthritis and ankylosing spondylitis). The protein that deposits in the brain of patients with Alzheimer's disease is a form of amyloid called beta-amyloid. In primary amyloidosis amyloid accumulate in one or more organ systems in the body. These light chain proteins are created in the bone marrow by malfunctioning plasma cells. Primary amyloidosis occurs by itself not associated with any other disease. Secondary amyloid is caused by a chronic infection or inflammatory disease such as rheumatoid arthritis, osteomyelitis, or granulomatous ileitis. Hereditary amyloidosis is a relatively uncommon cause of amyloidosis. The more common forms of amyloidosis are primary an secondary amyloidosis. However, hereditary amyloidosis is found worldwide. It occurs in families of nearly every ethnic background.
Amyotrophic Lateral Sclerosis (ALS) or Lou Gherig's Disease:  A classic motor neuron disease. Motor neuron diseases are progressive degenerative diseases of the nerves exiting the spinal cord which are responsible for supplying electrical stimulation to the muscles. This stimulation is necessary for the movement of body parts. ALS strikes in mid-life, most often in the fifth through seventh decades of life. Men are about one-and-a-half times more likely to have the disease as women.
ANA (Antinuclear Antibody):  An antibody directed against structures within the nucleus of the cell. ANAs are found in patients whose immune system is predisposed to cause inflammation against their own body tissues. Antibodies that are directed against one's own tissues are referred to as autoantibodies which is the more generic term and would include more than ANAs. This type of illness is called autoimmunity. ANAs indicate the possible presence of autoimmunity.
Anaerobic:  Not requiring oxygen. Anaerobic bacteria do not need oxygen to grow; in fact, oxygen is usually toxic to them. Fungi and yeast are anaerobic organisms. An anaerobic environment lacks oxygen. Anaerobic exercise relies on the metabolism of the sugar glucose to produce energy which uses "anaerobic pathways" which do not require oxygen. Weight lifting which leads to "burn" is an anaerobic exercise. Human metabolism is both aerobic and anaerobic reflecting the full range of metabolic pathways which have developed over 3+ billion years.
Analgesia:  The inability to feel pain.
Analgesic:  A drug that relieves pain.
Anaphia:  The inability to feel touch. A person with anaphia is said to be anaptic. From the Greek prefix an, not + Greek haphe, touch = inability to (feel) touch.
Anastomosis:  The connection of normally separate parts or spaces so they intercommunicate. An anastomosis may be naturally occurring or artificially constructed. An anastomosis may, for example, connect two blood vessel such as an artery and a vein or it may connect adjacent segments of the intestine. Anastomosis can develop as an embryological abnormality; it can develop as part of a disease process, and it can be surgically constructed.
Anatomy:  The study of form. While this word can related to the study of any structure, in medicine "anatomy" refers to the study of body form. Gross anatomy involves structures that can be seen with the naked eye as opposed to microscopic anatomy (or histology) which involves structures seen under the microscope. The word "anatomy" comes from the Greek ana- meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up.
Anatripsis:  The use of friction as a treatment modality for a medical condition. Anatripsis may or may not also involve the application of a medicine.
Ancylostoma infection:  Hookworm, an intestinal parasite that usually causes diarrhea or cramps. Heavy infestation with hookworm can be serious for newborns, children, pregnant women, and persons who are malnourished. Hookworm infections occur mainly in tropical and subtropical climates and affect about 1 billion people - about one-fifth of the world's population. One of the most common species of hookworm, Ancylostoma duodenale, is found in southern Europe, northern Africa, northern Asia, and parts of South America. A second species, Necator americanus, was once widespread in the southeastern US early in the 20th century.
Androgen:  A male sex hormone that promotes the development and maintenance of the male sex characteristics. The major androgen is testosterone.
Androgen insensitivity syndrome, complete:  A genetic disorder that makes XY fetuses insensitive to male hormones. Instead these males are born looking externally like normal females and they live their lives as females. Internally, there is a short blind-pouch vagina and no uterus, fallopian tubes or ovaries. There are testes in the abdomen or the inguinal canal. The complete androgen insensitivity syndrome is usually detected at puberty when a girl should begin to menstruate. Many of these individuals have no pubic or axillary hair. They have luxuriant scalp hair without male pattern balding. They are sterile and cannot bear children and are at high risk for osteoporosis and so should take estrogen replacement therapy.
Androgenic:  Pertaining to the development of male characteristics, including body hair, the genital organs and muscle mass. "Androgenic" is the adjective form of the noun "androgen," a word referring to any of the male hormones, including testosterone and androsterone.
Androphobia:  An abnormal and persistent fear of men. Sufferers experience anxiety even though they may realize they face no real threat. "Androphobia" is derived from the Greek andros (man) and phobos (fear).
Anemia:  The condition of having less than the normal number of red blood cells or less than the normal quantity of hemoglobin in the blood. The oxygen-carrying capacity of the blood is, therefore, decreased. Persons with anemia may feel fatigued easily, appear pale, develop palpitations and become unusually short of breath. Children with chronic anemia are prone to infections and learning problems. Anemia has four basic causes: (1) bleeding (hemorrhage), (2) excessive destruction of red blood cells (hemolysis), (3) underproduction (hypoplasia) of red blood cells, or (4) not enough normal hemoglobin.
Anemia, Addison:  Also known as pernicious anemia, is a blood disorder caused by a lack of vitamin B12. Patients who have this disorder do not produce the substance in the stomach that allows the body to absorb vitamin B12. This substance is called intrinsic factor. Pernicious anemia, is characterized by the presence in the blood of large, immature, nucleated cells (megaloblasts) that are forerunners of red blood cells. (Red blood cells, when mature, have no nucleus). It is thus a type of megaloblastic anemia.
Anemia, aplastic:  Anemia due to failure of the bone marrow to produce blood cells, including red and white blood cells as well as platelets. Aplastic anemia frequently occurs without a known cause. Causes of aplastic include chemicals, drugs, viruses, radiation, immune conditions (systemic lupus erythematosus, rheumatoid arthritis), pregnancy, paroxysmal nocturnal hemoglobinuria, and inherited disorders.
Anemia, Cooley’s:  Better known today as thalassemia (or as beta thalassemia or thalassemia major). Another name for the disease is Mediterranean anemia. Thalassa in Greek means the sea (like the Mediterranean Sea) + -emia means in the blood so thalassemia means sea in the blood. Thalassemia is not just one disease. It is a complex contingent of inherited disorders all of which involve underproduction of hemoglobin, the indispensable molecule in red blood cells that carries oxygen. In beta thalassemia, there is a mutation causing underproduction of hemoglobin, and profound anemia. The gene for beta thalassemia is relatively frequent in people of Mediterranean origin. Children with this disease inherit one gene from each parent. The parents are carriers (heterozygotes) with just one thalassemia gene, are said to have thalassemia minor, and are clinically normal. Their children affected with beta thalassemia seem entirely normal at birth because at birth we still have predominantly fetal hemoglobin. The anemia surfaces in the first few months after birth and becomes progressively more severe leading to pallor and easy fatigue, failure to grow, infections and diarrhea. Treatment based on blood transfusions is helpful but not curative. Gene therapy will, it is hoped, be applicable to this disease.
Anemia, iron deficiency:  The most common known form of nutritional disorder in the world, iron deficiency results in anemia because iron is necessary to make hemoglobin, the key molecule in red blood cells responsible for the transport of oxygen. In iron deficiency anemia, the red cells appear abnormal and are unusually small (microcytic) and pale (hypochromic). The pallor of the red cells reflects their low hemoglobin content. The prevalence of iron deficiency anemia is highest in children and women of childbearing age, especially pregnant women. In these women, iron deficiency increases the risk for a premature delivery and delivery of a low birth-weight baby. In children, iron deficiency causes developmental delays, behavioral disturbances, failure to thrive (grow) and increased infections.
Anemia, pernicious:  A blood disorder caused by a lack of vitamin B12. Patients who have this disorder do not produce the substance in the stomach that allows the body to absorb vitamin B12. This substance is called intrinsic factor (IF). Pernicious anemia is characterized by the presence in the blood of large, immature, nucleated cells (megaloblasts) that are forerunners of red blood cells. (Red blood cells, when mature, have no nucleus). It is thus a type of megaloblastic anemia.
Anemia, refractory:  Anemia (a shortage of red blood cells) unresponsive to treatment.
Anemia, sickle cell:  A genetic blood disease due to the presence of an abnormal form of hemoglobin, hemoglobin S. Sickle cell anemia affects millions of people throughout the world. It is particularly common among people whose ancestors came from sub-Saharan Africa; Spanish-speaking regions (South America, Cuba, Central America); Saudi Arabia; India; and Mediterranean countries, such as Turkey, Greece, and Italy. In the U.S., sickle cell disease occurs in about 1 in every 500 African-American births and 1 in every 1,000-1,400 Hispanic-American births. Sickle cell anemia is caused by an error in a gene that makes the beta globin chain of hemoglobin. The resultant abnormal hemoglobin (sickle hemoglobin) deforms the red blood cells (into a sickle shape) when they are under low oxygen conditions. Children who inherit 2 copies of the sickle gene, one from each parent, have sickle cell anemia. Children who inherit the sickle gene from only one parent do not have the disease, but will carry the sickle cell trait. Individuals with sickle cell trait generally have no symptoms. About 2 million Americans (or 1 in 12 African-Americans) carry the sickle gene.
Anencephaly:  A neural tube defect in embryological development that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th days of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp. Infants with this disorder are born without a forebrain, the largest part of the brain consisting mainly of the cerebrum, which is responsible for thinking and coordination. The remaining brain tissue is often exposed and is not covered by bone or skin.
Anergy:  A state of immune unresponsiveness induced when the T cell's antigen receptor is stimulated, effectively freezing T cell responses pending a "second signal" from the antigen-presenting cell. The delivery of the second signal by the antigen-presenting cell reverses anergy, provoking production of lymphokines necessary for the growth of additional T cells. T cells are small white blood cells that orchestrate and directly participate in the immune defenses. Also known as T lymphocytes, they are processed in the thymus (which is why they are called T cells), which is located just below the voice box.
Anesthesia:  Loss of feeling or awareness. A local anesthetic causes loss of feeling in a part of the body. A general anesthetic almost always puts the person to sleep, although occasionally it merely paralyzes the patient leaving full consciousness and sensation without the ability to respond. In the latter case, the ”anesthetic“ is not an anesthetic since sensation is preserved.
Anesthesiologist:  An anesthesiologist is a physician who is specialized in the practice of anesthesiology, the branch of medicine specializing in the use of drugs or other agents that cause insensibility to pain. (An anesthetist is a nurse or technician trained to administer anesthetics.)
Anesthesiology:  The branch of medicine specializing in the use of drugs or other agents that cause insensibility to pain.
Anesthetic:  A substance that causes lack of feeling or awareness.
Anesthetic, epidural:  An anesthetic injected into the epidural space surrounding the fluid-filled sac (the dura) around the spine which partially numbs the abdomen and legs. Commonly used in childbirth and referred to a an ”epidural“ or a ”caudal.“
Aneuploidy:  Normally, when s cell divides, each daughter cell receives an equal number of chromosomes. When this does not happen, it is termed aneuploidy. For example, three number 21 chromosomes or trisomy 21 (characteristic of Down syndrome) is a form of aneuploidy. One of the theories of cancer is that is is set in motion by aneuploidy later in life when there is an unequal division of chromosomes during cell division. The champion of this theory is the famous Peter Duesberg.
Aneurysm:  A localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture. The word ”aneurysm“ comes from the Greek aneurysma meaning ”a widening.“
Aneurysm, abdominal:  An aneurysm situated within the abdomen, usually involving the abdominal aorta, the large vessel coming directly from the heart. The full term for his condition is ”abdominal aortic aneurysm.“ Because of the volume of blood flowing under relatively high pressure within the aorta, a ruptured aneurysm of the aorta is a catastrophe usually resulting in death.
Aneurysm, arterial:  An aneurysm involving an artery. As opposed to a venous aneurysm or a cardiac aneurysm.
Aneurysm, arteriosclerotic:  An aneurysm that occurs because the vessel wall is weakened by arteriosclerosis. The correct term is atherosclerotic aneurysm since simple arteriosclerosis does not cause an aneurysm. Even among doctors, this mistake in terminology is common.
Aneurysm, berry:  A berry aneurysm is a small outpouching (aneurysm) that looks like a berry and classically occurs at the point at which a cerebral artery departs from the circular artery (the circle of Willis) at the base of the brain. Also called a ”brain aneurysm“ berry aneurysms often rupture and bleed. Survival from a ruptured berry aneurysm is about 50% and usually involves some serious neurological loss. Immediate surgical intervention is usually necessary.
Aneurysm, cardiac:  Bulging of an abnormally thin portion of the heart wall. Also called a heart aneurysm.
Aneurysm, dissecting:  An aneurysm in which the wall of an artery rips (dissects) longitudinally, splitting the layers of the artery. This occurs because bleeding into the weakened wall splits the wall. Dissecting aneurysms tend to affect the thoracic aorta. They are particularly common in Marfan’s disease and in any case are often fatal when they involve large vessels and require immediate surgical intervention.
Aneurysm, fusiform:  An aneurysm shaped like a spindle. A fusiform widening of an artery or vein. The word ”fusiform“ comes from the Latin ”fusus“ meaning ”spindle.“
Aneurysm, miliary:  An aneurysm shaped like a millet seed. (Millet is a cereal grass. Its seed is about 2 millimeters in diameter.) Miliary aneurysms tend to affect minute arteries in the brain and, in the eye, the retina.
Aneurysm, racemose:  An aneurysm which looks like a bunch of grapes. From the Latin racemus meaning ”a cluster or bunch, particularly of grapes.“
Aneurysm, renal:  An aneurysm involving the kidney.
Aneurysm, saccular:  An aneurysm which resembles a small sack. From the Latin ”sacculus“ meaning a small pouch. A berry aneurysm is typically saccular.
Aneurysm, thoracic:  An aneurysm situated within the thorax (chest).
Aneurysm, venous:  An aneurysm involving a vein. As opposed to an arterial aneurysm or a cardiac aneurysm.
Angiitis:  A rare inflammation of the blood vessels. There is a group of diseases that involve angiitis representing many different conditions. The actual cause of these conditions is usually not known, however, immune system abnormality is a common feature. Examples of angiitis include Kawasaki disease, Behcet's disease, polyarteritis nodosa, and Wegener's granulomatosis. Angiitis can also accompany infections (such as hepatitis B), exposure to chemicals (such as amphetamines and cocaine), cancers (such as lymphomas and multiple myeloma), and rheumatic diseases (such as rheumatoid arthritis, systemic lupus erythematosus). The word angiitis is derived from the Greek "a[n]geion", vessel + "-itis", inflammation. Another term for angiitis is vasculitis.
Angiitis, allergic granulomatous:  A disease (also often called the Churg-Straus syndrome) characterized by inflammation of the blood vessels in persons with a history of asthma or allergy. The symptoms of Churg-Strauss syndrome include fatigue, weight loss, inflammation of the nasal passages, numbness, and weakness. Treatment of Churg-Strauss syndrome involves stopping inflammation and suppressing the immune system.
Angina pectoris:  Chest pain that is typically severe and crushing with a feeling just behind the breastbone (the sternum) of pressure and suffocation, due to an inadequate supply of oxygen to the heart muscle. The term ”angina pectoris“ comes from the Latin angere meaning ”to choke or throttle“ + pectus meaning ”chest.“
Angina trachealis:  More commonly known as croup, this is an infection of the larynx, trachea, and the bronchial tubes that occurs mainly in children. It is usually caused by viruses, less often by bacteria. Symptoms include a cough that sounds like a barking seal and a harsh crowing sound during inhaling. As most parents are aware, the treatment is to expose the child to steam, commonly by turning on the hot water spigot of the bathroom shower and staying in the room with this child until relief occurs.
Angina, variant:  Chest pain due to coronary artery spasm, a sudden constriction of a coronary artery (one of the vessels that supply the heart muscle with blood rich in oxygen) depriving the heart muscle of blood and oxygen. Also called Printzmetal angina. Coronary artery spasm can be triggered by emotional stress, medicines, street drugs (cocaine) or exposure to cold. Treatments include beta- blocker medications and, classically, nitroglycerin to permit the coronary arteries to open up.
Angina, Vincent:  This is trench mouth, a progressive painful infection with ulceration, swelling and sloughing off of dead tissue from the mouth and throat due to the spread of infection from the gums. Certain germs (including fusiform bacteria and spirochetes) have been thought to be involved, but the full story behind this long-known disease is still not clear. This condition is also called Vincent (or Vincent's) angina after the French physician Henri Vincent (1862-1950). The word ”angina“ comes from the Latin ”angere“ meaning "to choke or throttle."
Angioedema:  Similar to hives but affects deeper skin layer. Hives (also called urticaria) are red, itchy, and raised areas of the skin of varying shapes and sizes. Hives are the result of histamine and other compounds that are released from cells called mast cells. Histamine causes serum to leak from the local blood vessels, which causes swelling in the skin.
Angioedema, hereditary:  A genetic form of angioedema. Persons with it are born lacking an inhibitor protein (called C1 esterase inhibitor) that normally prevents activation of a cascade of proteins leading to the swelling of angioedema. Patients can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box (larynx) which can compromise breathing.
Angiogenesis:  The process of developing new blood vessels. Angiogenesis is important in the normal development of the embryo and fetus. It also appears important to tumor formation. Certain proteins, including angiostatin and endostatin, secreted by tumors work (at least in mice) by interfering with the blood supply tumors need. Interfering with formation of blood supply to tumors is an area of cancer research and is the basis of the alternative treatment of cancer with shark and bovine cartilage. Development of new blood vessel channels in the adult is called neoangiogenesis.
Angiogram:  An x-ray image of the outline of the lumen (the inner space) of blood vessels which can be seen because the patient receives an injection of a radio-opaque dye (which stops x-rays and thus produces a negative image) to outline the vessels on the x-ray.
Angiography:  A procedure performed to view blood vessels after injecting them with a radio-opaque dye that outlines them on x-ray. This technique can be used to look at arteries in many areas of the body, including the brain, neck (carotids), heart, aorta, chest, pulmonary circuit, kidneys, gastrointestinal tract, and limbs.
Angiography, coronary:  A method used by mainstream medicine for evaluating and defining coronary artery disease (CAD). Coronary angiography is used to identify the location of CAD. A catheter (a hollow tube with a diameter of 2-3 mm.) is inserted through the skin into an artery in the groin or the arm. Guided with the assistance of a fluoroscope (a special x-ray viewing instrument), the catheter is then advanced to the opening of the coronary arteries, the blood vessels supplying blood to the heart where a small amount of radiographic contrast (a solution containing radioactive iodine, which is easily visualized by x-ray) is injected into each coronary artery. The images that are produced are called the angiogram. Angiographic images reveal a two dimensional view of any coronary arterial blockages which might be present. Coronary angiography is performed with the use of local anesthesia and intravenous sedation, and is generally not too uncomfortable. The procedure takes approximately 20-30 minutes. After the procedure, the catheter is removed and the artery in the leg or arm is sutured, "sealed," or treated with manual compression to prevent bleeding. There is a risk of serious complications from coronary angiography, as it is an "invasive" test, and this risk includes death. In skilled, experienced hands the statistical risk is below one per cent. While doctors claim to be able to read the "percentage blockage" using coronary angiography, double blind studies have shown that this is only a very rough estimate. Nevertheless, these "percentages" are used with patients as if they were hard scientific facts to be used in the decision making process involving more invasive procedures such as angioplasty and coronary bypass. The non-invasive alterative to the coronary angiogram is called the heart scan imaging technique.
Angiography, fluorescein:  A test to examine blood vessels in the retina, choroid, and iris of the eye. A special dye is injected into a vein in the arm and pictures are taken as the dye passes through the blood vessels in the eye. If the eye care professional (opthalmologist) suspects a patient has a disorder such as wet age-related macular degeneration (wet AMD), the patient may have fluorescein angiography. The resultant photos help evaluate leaking blood vessels and determine whether they can be treated.
Angioid streaks:  Tiny breaks in the elastin-filled tissue in the retina. These abnormalities are visible using a viewing instrument called an ophthalmoscope, commonly used in physical exams. Angioid streaks are seen in patients with pseudoxanthoma elasticum, a rare disorder of degeneration of the elastic fibers with tiny areas of calcification in the skin, retinae, and blood vessels. Angioid streaks can be associated with blindness.
Angiopathy:  Disease of the blood vessels (arteries, veins, and capillaries). There are two basic types of angiopathy: microangiopathy and macroangiopathy. In microangiopathy, the walls of small blood vessels become so thick and weak that they bleed, leak protein, and slow the flow of blood. For example, diabetics may develop microangiopathy with thickening of capillaries in many areas including the eye. In macroangiopathy, fat and blood clots build up in the large blood vessels, stick to the vessel walls, and block the flow of blood. Three locations of macroangiopathy are coronary artery disease (in the heart), cerebrovascular disease (in the brain), and peripheral vascular disease (affecting, for example, vessels in the legs).
Angioplasty:  Procedure with a balloon-tipped catheter to enlarge a narrowing in a coronary artery.
Angiosarcoma:  A cancer that begins in the lining of blood vessels which tends to be aggressive, recur locally, and spread widely. It can originate anywhere in the body but is well known to arise in skin, soft tissue, liver, breast, spleen, bone, lung and heart. Factors predisposing to angiosarcoma include chronic lymphedema (as from a radical mastectomy), radiotherapy, foreign materials (such as Dacron, shrapnel, steel, and plastic) in the body, and environmental agents (such arsenic solutions used to spray grapevines, the radiation-emitting contrast agent Thorotrast, and vinyl chloride in the plastic industry).
Angiostatin:  A fragment of a protein called plasminogen, used normally in blood clotting. This fragment is normally secreted by tumors and stops the process of developing new blood vessels (angiogenesis) which is necessary to tumor development. Angiostatin may represent a prototype for a new class of agents with which to treat cancer.
Angiotensin:  A family of peptides (smaller than proteins) that act as vasoconstrictors to narrow blood vessels.
Angle-closure glaucoma:  Increased pressure in the front chamber (anterior chamber) of the eye due to sudden (acute) or slowly progressive (chronic) blockage of the normal circulation of fluid within the eye. The block takes place at the angle of the anterior chamber formed by its junction of the cornea with the iris.
Anhedonia:  Loss of the capacity to experience pleasure. The inability to gain pleasure from normally pleasurable experiences. Anhedonia is a core clinical feature of depression, schizophrenia, and some other mental illnesses.
Anhidrosis:  The inability to sweat which is, of course, a problem, since to sweat is to be able to stay cool. Anhidrosis creates a dangerous inability to tolerate heat. From the Greek an- meaning not + hidros meaning sweat.
Aniline:  A chemical compound implicated, along with o-toluidine, in the causation of bladder cancer. Aniline and o-toluidine, both aromatic amines, are used in the manufacture of a variety of dyes, pharmaceuticals, pesticides, and chemicals employed in the manufacture of rubber. The primary routes of exposure to these compounds are inhalation and skin contact. There is no doubt that aniline and o-toluidine are carcinogens.
Anion gap:  A measure of the acidity of the blood resulting from a failure in the body's inability to adjust for the waste-products of excessive metabolic activity. It is measured by the interval between the sum of "routinely measured" cations minus the sum of the "routinely measured" anions in the blood. The anion gap = (Na+ + K+) - (Cl- + HCO3-) where Na- is sodium, K+ is potassium, Cl- is chloride, and HCO3- is bicarbonate. The anion gap can be normal, high, or low. A high anion gap indicates metabolic acidosis, the increased acidity of the blood due to metabolic processes. A low anion gap is relatively rare but may occur from the presence of abnormal positively charged proteins, as in multiple myeloma.
Anisocoria:  Both pupils of the eyes are usually of equal size. If they are not, that is termed anisocoria. The pupil may appear to open and close but it is really the iris (the colored part of the eye) that is the prime mover; the pupil is merely the absence of iris. The size of the pupil determines how much light is let into the eye. With anisocoria, the larger pupil lets more light enter the eye and there may, therefore, be photophobia (light sensitivity) on that side.
Anisometropia:  The condition in which the two eyes have an unequal refractive power. One eye may be myopic (nearsighted) and the other hyperopic (farsighted). Anisometropia is a serious concern in newborns and young children because it can lead to amblyopia (impaired vision in one eye). With a major degree of anisometropia, the brain is not able to reconcile the difference in images coming from the two eyes. It develops a preference for the image coming from one eye and suppresses the image from the other eye and, in time, the brain loses the ability to "see" the image from that eye.
Ankle-foot orthosis:  A brace (usually plastic) worn on the lower leg and foot to support the ankle, hold the foot and ankle in the correct position, and correct foot-drop. Abbreviated AFO. Also known as a foot-drop brace.
Ankyloglossia:  A minor congenital anomaly (birth defect) in which the flap of mucous membrane under the tongue (known as the frenum) is too short and limits the normal mobility of the tongue. Ankyloglossia is also called tongue tie from the folk belief that the anomaly causes feeding and speech problems. A child cannot feed or speak properly because the tongue is "tied." This belief is popular but unfounded.
Ankylosing spondylitis:  A type of arthritis that causes chronic inflammation of the spine. In the late stages the vertebrae fuse (ankylose) with each other. Thought to be an autoimmune disorder and over time, very debilitating.
Ankyrin deficiency:  Known also as hereditary spherocytosis, a genetic disorder of the red blood cell membrane clinically characterized by anemia, jaundice (yellowing) and splenomegaly (enlargement of the spleen), due to deficiency of ankyrin, a protein in the membrane of the red cell. In HS the red cells are smaller, rounder, and more fragile than normal. The red cells have a spherical rather than the biconcave-disk shape of the normal red cell. These rotund red cells (spherocytes) are osmotically fragile and less flexible than normal red cells and tend to get trapped in narrow blood passages, particularly in the spleen, and there they break up (hemolyze) leading to hemolytic anemia. The clogging of the spleen with red cells almost invariably causes splenomegaly.
ANLL, Acute Nonlymphocytic Leukemia:  More commonly called acute myeloid leukemia (AML). A quickly progressive malignant disease in which there are too many immature blood-forming cells in the blood and bone marrow.
Annular pancreas:  An abnormal ring of pancreas that encircles the duodenum and often causes intestinal obstruction.
Anomaly:  A deviation from the usual, something different, peculiar, or abnormal. A congenital anomaly is something that is unusual and different at birth.
Anomia or Anomic aphasia:  A problem with word finding. Impaired recall of words with no impairment of comprehension or the capacity to repeat the words. If you show such a person an egg, they cannot find the word "egg" but may say something like "from a chicken."
Anophthalmia:  Absence of the eye, as a result of a congenital malformation (birth defect) of the globe.
Anorexia nervosa:  An eating disorder characterized by markedly reduced appetite or total aversion to food. It is a serious psychological disorder and goes well beyond out-of-control dieting. Most often a girl or young woman, initially begins dieting to lose weight. Over time, the weight loss becomes a sign of mastery and control. The drive to become thinner is thought to be due to concerns about control and fears relating to one's body. The individual continues the endless cycle of restrictive eating, often to a point close to starvation. This becomes an obsession and can be a life-threatening condition.
Anorgasmia, or Anorgasmy:  Failure of a male or female to achieve an orgasm (climax) during sexual intercourse. Anorgasmia is characterized by psychologists as a "psychosexual dysfunction," a sexual maladjustment that is psychological or emotional in origin.
Anosmia:  Absence of the sense of smell, due to loss of the sense of smell or failure for it to develop which can be due to a number of things including swelling within the nose that prevents odors from gaining access to the olfactory area perhaps from a cold, allergy, or head trauma.
Anotia:  Absence of an ear. The term ”anotia“ usually refers to congenital absence of the external ear, the auricle, the visible part of the ear.
Anovular menstruation:  Menstruation that occurs without ovulation. The egg stays in the ovary.
Anoxia:  Lack of oxygen.
Antagonist:  In biochemistry, an antagonist acts against and blocks an action. For example, insulin lowers the level of glucose (sugar) in the blood, whereas another hormone called glucagon raises it; therefore, insulin and glucagon are antagonists.
Antegrade amnesia:  Amnesia in which the lack of memory relates to events occurring after a traumatic occurrence.
Antenatal surgery:  The surgical treatment of the fetus before birth. Also called prenatal surgery or, most often, fetal surgery. Fetal surgery is done when the fetus is not expected to live long enough to make it through to delivery or to live long after birth unless fetal surgery is performed.
Anterior:  The front, as opposed to the posterior. The anterior surface of the body is the chest and abdomen, etc.
Anterior chamber:  The space in the eye that is behind the cornea and in front of the iris.
Anterior cruciate ligament:  A ligament in the knee that crosses from the underside of the femur (the thigh bone) to the top of the tibia (the bigger bone in the lower leg). Abbreviated ACL. Injuries to the ACL can occur in a number of situations, including sports, and can be rather serious, requiring surgery.
Anterior pituitary:  The front portion of the pituitary, a small gland in the head called the master gland. Hormones secreted by the anterior pituitary influence growth, sexual development, skin pigmentation, thyroid function, and adrenocortical function. These influences are exerted through the effects of pituitary hormones on other endocrine glands except for growth hormone which acts directly on cells.
Anterograde memory:  Loss of short-term memory with retention of memories from the distant past (long-term memory).
Anteroposterior:  From front to back, abbreviated AP. When a chest x-ray is taken with the back against the film plate and the x-ray machine in front of the patient it is called an anteroposterior (AP) view. As opposed to from back to front (which is called posteroanterior or PA).
Anthophobia:  An abnormal and persistent fear of flowers. Sufferers experience anxiety even though they realize they face no threat from flowers. Any genus or species of flowers can instill fear, as can any flower part, such as a petal or stem.
Anthracycline:  A member of a family of chemotherapy drugs that are also antibiotics. The anthracyclines act to prevent cell division by disrupting the structure of the DNA and terminate its function. The anthracyclines are frequently used in leukemia therapy. The anthracyclines include daunorubicin (Cerubidine), doxorubicin (Adriamycin, Rubex), epirubicin (Ellence, Pharmorubicin), and idarubicin (Idamycin).
Anthrax:  A serious bacterial infection caused by Bacillus anthracis that occurs primarily in animals. Cattle, sheep, horses, mules, and some wild animals are highly susceptible. Humans and swine are generally quite resistant to anthrax. Humans become infected when the spores of B. anthracis enter the body by contact with animals infected with B. anthracis or from contact with contaminated animal products, insect bites, ingestion, or inhalation. Aerosolized ("weaponized") spores of B. anthracis can potentially be used for biological warfare and bioterrorism. Cutaneous anthrax is the most common form of the disease and is characterized by the development of a localized skin lesion with a central lesion surrounded by marked edema (swelling). Inhalation anthrax (woolsorters' disease) typically involves hemorrhagic mediastinitis (bleeding into the mid-chest), rapidly progressive systemic (bodywide) infection, and carries a very high mortality rate. Gastrointestinal anthrax is much more rare but is also associated with a high mortality rate.
Anthrax immunization:  A series of six shots over six months and booster shots annually, the anthrax vaccine now in use in the U.S. was first developed in the 1950s and approved by the Food and Drug Administration for general use in 1970. It is given routinely to veterinarians and others working with livestock. In December, 1997 it was announced that all US military would receive the vaccine, as do the military in the UK and Russia due to concern that anthrax might be used in biological warfare.
Anthrax toxin:  The toxic substance secreted by the bacterium Bacillus anthracis, the causative agent of the disease anthrax. Anthrax toxin is made up of three proteins. One is protective antigen and two are enzymes that are called edema factor and lethal factor. The protective antigen binds to surface receptors on the host's cell membranes. After being cleaved by a protease, protective antigen binds to the two toxic enzymes and mediates their transport into the cytosol (the soluble portion of the cytoplasm) where they exert their pathogenic (disease-causing) effects. Lethal factor is the crucial pathogenic enzyme. It is the killer in the toxin.
Anti-angiogenesis drugs:  These drugs, which include angiostatin and endostatin, halt the process of developing new blood vessels (angiogenesis). Angiostatin is a piece of a larger and very common protein, plasminogen, that the body uses in blood clotting. Endostatin is a piece of a different protein, collagen 18, that is in all blood vessels. Both angiostatin and Endostatin are normally secreted by tumors. It is hoped that they will provide the basis for a new class of agents to treat cancer. The original idea of combating cancer in this way came from nutritional medicine about 1990 when shark cartilage was found to contain anti-angiogenesis properties. Following that discovery the pharmaceutical industry has been hot on the trail of drugs which may be patentable and have these characteristics.
Anti-platelet agents:  Medications that, like aspirin, reduce the tendency of platelets in the blood to clump and clot.
Antibacterial:  Anything that destroys bacteria or suppresses their growth or their ability to reproduce. Heat, chemicals (chlorine), and antibiotic drugs all have antibacterial properties.
Antibiotic:  A drug used to treat bacterial infections. The original definition of an antibiotic was a substance produced by one microorganism that selectively inhibits the growth of another microorganism. However, wholly synthetic antibiotics (usually chemically related to natural antibiotics) have since been produced that accomplish comparable tasks.
Antibiotic resistance:  The ability of bacteria and other microorganisms to withstand an antibiotic to which they were once sensitive (and were once stalled or killed outright). Also called drug resistance.
Antibody:  An immunoglobulin, a specialized immune protein, produced because of the introduction of an antigen into the body, and which possesses the remarkable ability to combine with the very antigen that triggered its production. The production of antibodies is a major function of the immune system and is carried out by a type of white blood cell called a B cell (B lymphocyte). Antibodies can be triggered by and directed at foreign proteins, microorganisms, or toxins. Some antibodies are auto-antibodies and attack the host's own tissues producing autoimmune disease, for example lupus erythematosis.
Anticholinergic:  The action of certain medications that inhibit the transmission of parasympathetic nerve impulses and thereby reduce spasms of smooth muscle (such as that, for example, in the bladder) as well as a range of vegetative (digestive and circulatory) functions thus producing side effects.
Anticipation:  A remarkable phenomenon in which a genetic disease appears earlier and with increased intensity with each succeeding generation. Anticipation was once thought not to exist in genetics. However, it has now been proven to occur in a large number of important genetic disorders, including Huntington's disease and myotonic dystrophy. In molecular terms, anticipation is due to the expansion of a trinucleotide repeat sequence in the DNA. This phenomenon also occurs in the fragile X syndrome, the most common inherited form of mental retardation.
Anticoagulant:  Any agent used to prevent the formation of blood clots.
Anticonvulsant:  A medication used to control (prevent) seizures (convulsions) or stop an ongoing series of seizures.
Antidiabetic agent:  A substance that helps a person with diabetes control their level of glucose (sugar) in the blood. Antidiabetic agents include insulin and the oral hypoglycemic agents and there are many nutritional compounds with this characteristic which are roundly ignored in mainstream medicine.
Antidiuretic hormone (ADH):  A small peptide molecule that is released by the pituitary gland at the base of the brain after being made nearby in the hypothalamus. ADH has an antidiuretic action by promoting the concentration of urine. Inappropriate secretion of ADH results in the inability to put out dilute urine, disturbs fluid and electrolyte balance, and causes nausea, vomiting, muscle cramps, confusion and convulsions. This syndrome may occur in association with oat-cell lung cancer, pancreatic cancer, prostate cancer, and Hodgkin's disease as well as a number of other disorders. ADH also can stimulate contraction of arteries and capillaries and can cause hypertension. ADH is also known as vasopressin.
Antidote:  An agent that counteracts a poison and neutralizes its effects. A chemical antidote is a substance that unites with a poison to form a harmless chemical compound. A mechanical antidote is a substance that prevents the absorption of a poison from the intestine into the body.
Antiestrogen:  A substance that can prevent the full expression of estrogen. Antiestrogens act by exerting antagonistic effects on target tissues (DHEA and testosterone act in this way) or by competing with estrogens for access to receptor sites located on the cell surface. An example of this is the drug tamoxifen, an antiestrogen that is used in the treatment of breast cancer and to reduce the breast cancer incidence in high-risk women.
Antifungal:  A drug used to treat fungal infections. Examples of antifungal drugs include Monostat and Lamisil.
Antigen:  A substance that is capable of causing the production of an antibody. Antigens may or may not lead to an allergic reaction. Allergens are antigens that cause an allergic reaction and the production of IgE (immunoglobulin E).
Antihistamines:  Drugs that combat the histamine released during an allergic reaction by blocking the action of the histamine on the tissue. Antihistamines do not stop the formation of histamine nor do they stop the conflict between the IgE and antigen. Therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects.
Antihypertensive:  Something that reduces high blood pressure (hypertension).
Antiinfective:  Something capable of acting against infection, by inhibiting the spread of an infectious agent or by killing the infectious agent outright. Anti-infective is a general term that encompasses antibacterials, antibiotics, antifungals, antiprotozoans and antivirals.
Antimalarial:  A drug directed against malaria. The original antimalarial agent was quinine which took its name from the Peruvian Indian word "kina" meaning "bark of the tree." A large and complex molecule, quinine is the most important alkaloid found in cinchona bark. Until World War I, it was the only effective treatment for malaria. In fact, quinine was the first chemical compound to be successfully used to treat an infectious disease.
Antimetabolite:  A drug that inhibits a normal metabolic process. Examples of antimetabolites include 6-mercaptopurine (6MP), methotrexate, and hydroxyurea.
Antimicrobial:  A drug used to treat a microbial infection; a general term that refers to a group of drugs that includes antibiotics, antifungals, antiprotozoals, and antivirals.
Antimony:  A metal high levels of which can be toxic. Antimony occurs naturally in the earth. Antimony ores are mined and then mixed with other metals to form antimony alloys or combined with oxygen to form antimony oxide. Antimony breaks easily, but when mixed into alloys, it is used in lead storage batteries, solder, sheet and pipe metal, bearings, castings, and pewter. Antimony oxide is added to textiles and plastics to prevent them from catching fire and is also used in paints (especially enamels), ceramics, and fireworks. Antimony is released into the environment from natural sources and industry.
Antineoplastic:  Acting to prevent, inhibit or halt the development of a neoplasm (a tumor). An agent with antineoplastic properties.
Antinuclear antibody:  An antibody that is directed against structures within the nucleus of the cell. Antinuclear antibodies (ANAs) are found in people whose immune system is predisposed to cause inflammation against their own body tissues. Antibodies that are directed against one's own tissues are referred to as autoantibodies. The propensity for the immune system to work against its own body is referred to as autoimmunity. A positive test for ANAs indicates the possible presence of autoimmunity.
Antioxidant:  Any substance that reduces oxidative damage by regulating oxidation and reduction. Living metabolism is created by oxidation and reductions. The are complimentary processes and must be in balance to create health. Redox reactions involve the exchange of electrons. An atom which loses an electron is called a free radical and is highly toxic to surrounding molecules. . Antioxidants have electrons to spare and can remedy the situation.
Antiparasitic:  Effective in the treatment of parasites.
Antiphospholipid antibody syndrome (APLS):  An immune disorder characterized by the presence of abnormal antibodies in the blood associated with abnormal blood clotting, migraine headaches, recurrent pregnancy losses (repeat spontaneous abortions), and low blood platelet counts (thrombocytopenia). These abnormal antibodies are directed against phospholipids. (fats that contains phosphorous). APLS can occur by itself (primary) or be caused by an underlying condition such as systemic lupus erythematosus. About a third of persons with primary APLS have heart valve abnormalities.
Antiprotozoal:  Something that destroys protozoa or inhibits their growth and ability to reproduce. A protozoa is single-cell organism, many times larger than bacteria, that can only reproduce within a host organism. A few of the protozoa of medical importance include Plasmodium vivax (the cause of malaria); Entamoeba histolytica (the cause of amebiasis, amebic dysentery); Entamoeba coli, one of the most common undetected parasitic conditions; Trichomonas vaginalis (a cause of vaginal infection); and Pneumocystis carinii (a common cause of pneumonia in immunodeficient persons).
Antipsychotic:  A medication (or another measure) that is believed to be effective in the treatment of psychosis. For example, Thorazine was the first widely accepted antipsychotic medication used to treat schizophrenia.
Antipyretic:  Something that reduces fever or quells it. There are 3 classes of antipyretic medications that are sold over-the-counter without prescription: Salicylates -- aspirin (acetylsalicylic acid), choline salicylate (Arthropan), magnesium salicylate (Arthriten), and sodium salicylate (Scot-Tussin Original); Acetaminophen (Tylenol); and Nonsteroidal anti-inflammatory drugs (NSAIDs) -- ibuprofen (Advil), naproxen (Naprosyn, Aleve), and ketoprofen.
Antiretroviral:  An agent or process effective against a retrovirus. For example, a drug to treat HIV.
Antiretroviral therapy (ART):  Treatment that suppresses or stops a retrovirus. One of the retrovirus is the human immunodeficiency virus (HIV) that is associated with AIDS. Retroviruses are so named because they carry their genetic information in the form of RNA rather than DNA so that the information must be transcribed in "reverse" direction, from RNA into DNA.
Antispasmodic:  A medication that suppresses or prevents muscle spasms.
Antithymocyte globulin:  An immuno-suppressive agent that specifically destroys T lymphocytes. Abbreviated ATG. ATG is the gamma globulin fraction of antiserum from animals that have been immunized against human thymocytes. Uses of ATG include the treatment of transplant rejection, aplastic anemia, and other conditions in which immuno-suppression may be indicated.
Antithyroid antibody:  An antibody directed against the thyroid gland, a gland which produces thyroid hormones such as, for example, thyroxine (T4) and triiodothyronine(T3). Antithyroid antibodies can be associated with inflammation of the thyroid gland and affect its function. Antithyroglobulin and antimicrosomal antibodies are examples of antithyroid antibodies. Hashimoto’s disease in a commonly occurring example of this type or disorder.
Antithyroid drug:  A drug directed against the thyroid gland. The antithyroid drugs include carbimazole, methimazole, and propylthiouracil (PTU). These drugs are used to treat hyperthyroidism (overactivity of the thyroid gland) in order to reduce the excessive thyroid activity before surgery and to treat and maintain patients not having surgery.
Antitoxin:  An antibody capable of destroying a toxin made by microorganisms. An antitoxin provides passive immunity. For example, if a child gets whooping cough, an antitoxin prepared in horses against diphtheria may be useful in treatment. The antitoxin can only be of short-term value because the antibodies against diphtheria were made by the horse and the child is just the passive recipient of the antibodies. A ”toxin,“ in this sense, is one of a number of poisons produced by certain plants, animals, and bacteria usually referring to a particular protein produced by some higher plants, animals and pathogenic bacteria. A toxin typically has a high molecular weight (as compared to a simple chemical poison), is antigenic (elicits an antibody response), and is highly poisonous to living creatures.
Antiviral:  An agent that kills a virus or that suppresses its ability to replicate and, hence, inhibits its capability to multiply and reproduce. For example, amantadine (Symmetrel) is a synthetic antiviral. It acts by inhibiting the multiplication of the influenza A virus.
Antrum:  A general term for cavity or chamber which may have specific meaning in reference certain organs or sites in the body. The antrum of the stomach (gastric antrum) is a portion before the outlet to the duodenum which is lined by mucosa which does not produce acid.
Anxiety:  A feeling of apprehension and fear characterized by physical symptoms such as palpitations, sweating, and feelings of stress.
Anxiety disorder:  A chronic condition characterized by an excessive and persistent sense of apprehension with physical symptoms such as sweating, palpitations, and feelings of stress. Anxiety disorders have biological and environmental causes. Anxiety disorders are very common, affecting one in 10 Americans.
Anxiety disorder, social:  Excessive fear of embarrassment in social situations that is extremely intrusive and can have debilitating effects on personal and professional relationships. Also called social phobia. Phobias are persistent, irrational fears of certain objects or situations. They recognize that their fear may be excessive or unreasonable, but are unable to overcome it. The symptoms and signs of social phobia include blushing, sweating, trembling, rapid heartbeat, muscle tension, nausea or other stomach discomfort, lightheadedness, and other symptoms of anxiety.
Aorta:  The largest artery in the body, the aorta arises from the left ventricle of the heart, goes up a little ways, bends over, then descends through the chest and through the abdomen and ends by dividing into two arteries called the common iliac arteries that go to the legs.
Aortic aneurysm:  An aneurysm is a localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture. An aortic aneurysm is an outpouching, a local widening (aneurysm) of the largest artery in the body, the aorta (which comes directly from the heart), involving that vessel in its course above the diaphragm (thoracic aortic aneurysm) or, more commonly, below the diaphragm (abdominal aortic aneurysm). Because of the volume of blood flowing under relatively high pressure within the aorta, a ruptured aneurysm of the aorta is a catastrophe.
Aortic arch:  The aortic arch is the second section of the aorta, the largest artery in the body. The aorta arises from the left ventricle of the heart and first goes up, then bends, and goes down. The part that goes up is termed the ascending aorta, the part that bends is the arch of the aorta, and the part that goes down is the descending aorta.
Aortic atresia:  Congenital absence of the normal valvular opening from the left ventricle of the heart into the aorta. This is a condition inconsistent with life.
Aortic insufficiency (regurgitation):  Backflow of blood back down from the aorta into the left ventricle of the heart due to incompetency of the aortic valve.
Aortic stenosis:  Narrowing (stenosis) of the heart valve between the left ventricle of the heart and the aorta. This narrowing impedes the delivery of blood through the aorta to the body. A normal aortic valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid), which are thick. stiff and stenotic. Some children with aortic stenosis have chest pain, unusual fatigue, dizziness or fainting. Many children have few or no symptoms.
Aortic valve:  One of the four valves in the heart, this valve is situated at exit of the left ventricle of the heart where the aorta (the largest of all arteries) begins. The aortic valve lets blood from the left ventricle be pumped up (ejected) into the aorta but prevents blood once it is in the aorta from returning to the heart.
Aperient:  Laxative. Used both as a noun (an aperient is a laxative) and adjective (prunes are an aperient fruit). From the Latin "aperiens" meaning to uncover, open (in this case, the bowels)
Apex:  From the Latin meaning summit, the apex is the tip of a pyramidal or rounded structure, like the lung or the heart. The apex of the lung is indeed its tip, its rounded most superior portion. It can be auscultated (listened to with a stethoscope) in the recess just above the collar bone. The apex of the heart is likewise its tip, but that is formed by the left ventricle so it is essentially the most inferior portion of the heart.
Apgar score:  Named for the preeminent American anesthesiologist Virginia Apgar (1909-1974) who invented the scoring method in 1952, a practical method of evaluating the physical condition of a newborn infant shortly after delivery. The Apgar score is a number arrived at by scoring the heart rate, respiratory effort, muscle tone, skin color, and response to a catheter in the nostril. Each of these objective signs can receive 0, 1, or 2 points. A perfect Apgar score of 10 means an infant is in the best possible condition. An infant with an Apgar score of 0-3 needs immediate resuscitation. The Apgar score is done routinely 60 seconds after the birth of the infant and then it is commonly repeated 5 minutes after birth. In the event of a difficult resuscitation, the Apgar score may be done again at 10, 15, and 20 minutes. An Apgar score of 0-3 at 20 minutes of age is predictive of high rates of morbidity (disease) and mortality (death).
Aphagia:  Inability to eat. From the Greek prefix ”a-” meaning ”not“ + ”phago“ meaning ”to eat“ + not to eat.
Aphakia:  Absence or loss of the eye's natural crystalline lens, as after cataract removal. From a-, without + phacos, the Greek word for a lentil bean. The ancients thought (quite correctly) that the lens of the eye was shaped like a lentil bean.
Aphasia:  Literally aphasia means no speech. Aphasia can apply to a defect in expression or comprehension.
Apheresis:  The process of removing a specific component from blood and returning the remaining components to the donor for therapeutic purposes. Also called hemapheresis or pheresis.
Aphonia:  Inability to speak.
Aphrasia:  The inability to speak or understand phrases
Aphthous ulcer:  A small sensitive painful ulcer crater in the lining of the mouth. Commonly called a canker sore. Aphthous ulcers typically last for 10-14 days and they heal without leaving a scar. There are many possible causes of aphthous ulcers.
Apical:  The adjective for apex, the tip of a pyramidal or rounded structure, like the lung or the heart. For example, an apical lung tumor is a tumor located at the top of the lung.
Apiphobia:  Fear of bees.
Aplasia:  Failure to develop. If something develops and then wastes away, that is atrophy.
Aplasia of the breast (also called amastia):  A rare condition wherein the normal growth of the breast or nipple never takes place. They are congenitally absent. There is no sign whatsoever of the breast tissue, areola or nipple.
Aplastic Anemia:  Anemia due to failure of the bone marrow to produce blood cells, including red and white blood cells as well as platelets. Aplastic anemia frequently occurs without a known cause. Known causes include exposure to chemicals (benzene, toluene in glues, insecticides, solvents), drugs (chemotherapy, gold, seizure medications, antibiotics, and others), viruses (HIV, Epstein-Barr), radiation, immune conditions (systemic lupus erythematosus, rheumatoid arthritis), pregnancy, paroxysmal nocturnal hemoglobinuria, and inherited disorders (Fanconi's anemia).
Apnea:  The absence of breathing (respirations). There are three type forms of apnea: blockage of the airways, cessation of respiratory effort (usually brain-related and referred to as "central apnea"), and a combination of airways blockage and central apnea.
Apolipoprotein E:  A gene that codes for a protein in lipoproteins (complexes of fat + protein) that are normal constituents of blood plasma, namely, chylomicrons, HDL (high density lipoprotein), LDL (low density lipoprotein), and VLDL (very low density lipoprotein). The abbreviation for apolipoprotein E is ApoE. Studies of families in which Alzheimer disease tends to develop at later ages have shown that the disease is unusually frequent in persons with a particular variant form of ApoE termed ApoE4 present in only a minority of the general population. However, family studies suggest that the ApoE gene locus is neither necessary nor sufficient to cause Alzheimer disease and may simply modify the preclinical progression, and therefore the age of onset, in people otherwise predisposed to develop Alzheimer disease. The ApoE gene is now known to be on chromosome 19.
Apophysitis calcaneus:  Also called Sever's condition, this disorder is due to inflammation of the growth plate of the calcaneus, the bone at the back of the heel. The inflammation is at the point where the Achilles tendon attaches. It occurs mainly in older children and adolescents, especially active boys. It can be very painful. It is one of those conditions often dismissed as "growing pains." When this condition flares up, it is treated with activity limitation, medication, shoe inserts, heel lifts, and sometimes casting when it becomes especially severe. However, fortunately, the condition is usually self-limited and disappears as the child gets older. Apophysitis refers to inflammation of the apophysis, the bony protuberance, of the calcaneus.
Apoplexy:  An old term for a stroke, also termed a cerebrovascular accident (or CVA), often associated with loss of consciousness and paralysis of various parts of the body. The word "apoplexy" comes from the Greek apoplexia meaning a seizure, in the sense of being struck down. The ancients believed that someone suffering a stroke (or any sudden incapacity) had been struck down by the gods.
Apoptosis:  A form of cell death in which a programmed sequence of events leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells. The human body replaces perhaps a million cells a second. Too little or too much apoptosis plays a role in a great many diseases. When programmed cell death does not work right, cells that should be eliminated may hang around and become immortal. For example, in cancer and leukemia. When apoptosis works overly well, it kills too many cells and inflicts grave tissue damage. This is the case in degenerative disorders such as arthritis, strokes and neurodegenerative disorders such as Alzheimer, Huntington and Parkinson diseases. Apoptosis is also called programmed cell death or cell suicide.
Appendectomy:  Removal by surgery of the appendix, the small worm-like appendage of the colon (the large bowel). An appendectomy is performed because of probable appendicitis, inflammation of the wall of the appendix generally associated with infection.Appendicitis usually is suspected because of the medical history and physical examination. The pain of developing appendicitis is at first diffuse and poorly localized but as the inflammation extends through the appendix to its outer covering and then to the lining of the abdomen, the pain changes and becomes localized to one small area between the front of the right hip bone and the belly button. The exact point is named after Dr. Charles McBurney - McBurney's point. If the appendix ruptures and infection spreads throughout the abdomen, the pain becomes diffuse again as the entire lining of the abdomen becomes inflamed. Ultrasound and computerized tomography (CT scan) also may be helpful in diagnosis. Due to the varying size and location of the appendix and the proximity of other organs to the appendix, it may be difficult to differentiate appendicitis from other intra-abdominal diseases. The treatment for appendicitis is antibiotics and surgical removal of the appendix (appendectomy). Complications of appendectomy include wound infection, abscess, and obstruction of the intestine. The first successful appendectomy was done in Davenport, Iowa in 1885 by Dr. William West Grant.
Appendix:  A small outpouching from the beginning of the large intestine (the ascending colon). Also called the appendix vermiformis because of it worm-like structure.
Appendix cancer:  A malignancy of the appendix, accounting for about 1 in 200 of all gastrointestinal malignancies. The most common type of appendiceal cancer is carcinoid tumor with adenocarcinoma next. Tumors of the appendix often present with peritoneal seeding of the malignant cells. Advances in treatment have raised survival rates to about 80%.
Appendix epididymis:  A small cystic projection from the surface of the epididymis which represents a remnant the embryologic mesonephros (middle kidney). The epididymis is a structure within the scrotum attached to the backside of the testis. The epididymis is a coiled segment of the spermatic ducts that serves to store, mature and transport spermatozoa.
Appendix epiploica:  A finger-like projection of fat attached to the colon.
Appendix testis:  A small solid projection of tissue on the outer surface of the testis which is a remnant of the embryologic Mullerian duct.
Apposition:  The word "apposition" has several senses including the act of adding or accretion and also the putting of things in juxtaposition, or side by side. Growth by apposition is a mode of growth that is characteristic of many tissues in the body by which nutritive matter from the blood is transformed on the surface of an organ into solid unorganized substance. To lose a pair of apposed teeth is to lose teeth that are next to one another, teeth that are juxtaposed, i.e. next to each other.
Apraxia:  The inability to execute a voluntary motor movement despite being able to demonstrate normal muscle function. Apraxia is not related to a lack of understanding or to any kind of physical paralysis but is caused by a problem in the cortex of the brain. This could happen, for example, after a stroke or as a consequence of a brain tumor. An example would be the inability to grasp a cup of tea and transport it to one's lips.
Apraxia of speech:  A severe speech disorder characterized by inability to speak, or a severe struggle to speak clearly. Apraxia of speech occurs when the oral- motor muscles do not or cannot obey commands from the brain, or when the brain cannot reliably send those commands.
APS (autoimmune polyglandular syndrome):  A genetic autoimmune disease with an extraordinary array of clinical features but characterized most often by at least 2 of the following 3 findings: (1) hypoparathyroidism -- underfunction of the parathyroid glands which control calcium, (2) candidiasis (yeast infection), and (3) adrenal insufficiency (underfunction of the adrenal gland). APS was the first systemic (bodywide) autoimmune disease found due to a defect in a single gene. The child with APS develops problems in numerous glands (polyglandular) including hypoparathyroidism, hypogonadism (with sex gland failure), adrenal insufficiency, type 1 (insulin-dependent) diabetes with insufficient insulin production by the pancreas gland, and latent hypothyroidism (underfunction of the thyroid gland). Other features of APS are total baldness (alopecia totalis), inflammation of the cornea and whites of the eye (keratoconjunctivitis), underdevelopment (hypoplasia) of the enamel of the teeth, childhood-onset moniliasis (yeast infection), juvenile-onset pernicious anemia, gastrointestinal problems (malabsorption, diarrhea), and chronic active hepatitis.
Aquaphobia:  An abnormal and persistent fear of water. Sufferers from aquaphobia experience anxiety even though they realize the water in an ocean, a river, a lake, a creek or even a bathtub may pose no imminent threat. They generally avoid such activities as boating and swimming. Around the house, they may fear the water in a shower or tub and even desist from bathing therein.
Aqueduct:  A channel for the passage of fluid.
Aqueduct of Sylvius (Aqueduct of the midbrain):  A canal between two of the cavities (called the third and fourth ventricles) in the brain through which cerebrospinal fluid passes.
Aqueous humor:  The fluid normally present in the anterior and posterior chambers of the eye(which are separated by the iris). It is a clear, watery fluid that flows between and nourishes the lens and the cornea; it is secreted by the ciliary processes.
Arachnodactyly:  Long spider-like fingers and toes, a frequent finding in Marfan's syndrome, a heritable disorder of connective tissue. President Lincoln is thought to have had Marfan's syndrome. "Arachnodactyly" is derived from the Greek "arachne" (spider) and "daktylos" (finger).
Arachnoid:  The middle layer of the three layers of connective tissue protecting th brain and spinal cord (the pia mater, the arachnoid, and the dura mater). The word itself means "spider-like" referring to the appears of the structure which reminds one of a find spider-web mesh.
Arachnoiditis:  Inflammation of the middle layer of membranes covering the brain and spinal cord. Arachnoiditis can occur as a complication of procedures such as myelograms, spinal operations, epidural steroid injections, and injury to the spine.
Arachnophobia:  An abnormal and persistent fear of spiders. Sufferers from arachnophobia experience undue anxiety even though they realize the risk of encountering a spider and being harmed by it is small or nonexistent. They may avoid going barefoot and may be especially alert when taking showers or getting into and out of bed.
Arboviral encephalitis:  Inflammation of the brain (encephalitis) caused by infection with an arbovirus, a virus transmitted by a mosquito, tick or another arthropod. Infection of vertebrates, including humans, occurs when an infected arthropod feasts upon them for a blood meal. There are a number of types of arboviral encephalitis. All of these are transmitted by mosquitoes.
Arbovirus:  Arboviruses are transmitted to humans by mosquitoes and ticks (arthropods). It comes from the first two letters of arthropod + the first two letters of bourne. Arboviruses are transmitted (borne) to humans by mosquitoes and ticks (arthropods).
Archaea:  A unique group of microorganisms classified as bacteria (Archaeobacteria) but genetically and metabolically different from all other known bacteria. They appear to be living fossils, the survivors of an ancient group of organisms. The name Archaea comes from the Greek archaios meaning ancient.
Archaeogenetics:  The study of the past using the techniques of molecular genetics. The application of genetics to archeology. The word comes from the Greek archaios (ancient) + genetics = archaeogenetics, literally, ancient genetics. In archaeogenetics, information on the DNA of different ethnic groups from around the world is used to analyze prehistoric events and corroborate accounts from historical sources. The DNA data are reconciled with the findings of archeologists, linguists, and paleoanthropologists to shed light on the past.
Arcus senilis:  A cloudy opaque arc or circle around the edge of the eye, often seen in the eye of the elderly.
ARD:  Acronym that stands for a disorder known as Adult Respiratory Distress or Acute Respiratory Distress. Also referred to as ARDS (ARD Syndrome). In ARD there is respiratory failure of sudden (acute) onset due to the rapid accumulation of fluid in the lungs (pulmonary edema) following an abrupt increase in the permeability of the normal barrier between the capillaries and the air sacs in the lungs. ARD is the most serious response to acute lung injury.
Areflexia:  Absence of neurologic reflexes such as the knee jerk reaction.
Areola:  The small darkened area around the nipple of the breast.
Argentaffinoma:  A tumor which secretes large amounts of the hormone serotonin. Argentaffinoma is also called carcinoid tumor. The tumor usually arises in the gastrointestinal tract, anywhere between the stomach and the rectum (often the appendix) and from there may metastasize to the liver. In the liver the tumor produces and releases large quantities of serotonin into the blood. The consequences are called the carcinoid syndrome. It is directly due to the serotonin and includes flushing and blushing, swelling of the face (especially around the eyes), flat angiomas (little collections of dilated blood vessels) on the skin, diarrhea, bronchial spasm, rapid pulse, low blood pressure and narrowing of the valves of the heart, often with regurgitation (backflow of blood). One or more of four kinds of treatment are used for carcinoid tumors: surgery (to take out the cancer); radiation therapy (using high-dose x-rays to kill the cancer cells); biological therapy (using the body's natural immune system to fight the cancer); and chemotherapy (using drugs to kill cancer cells).
Arginine:  An amino acid, one of the 20 amino acids that serve as the building blocks in protein. Arginine is not an "essential" amino acid. It is not essential to the diet, but can be made by the body from other substances. However, it is usually considered essential to the diet for children so they can grow normally. Lack of arginine in the diet impairs growth and in adult males it decreases the sperm count. Arginine is available in foods such as turkey, chicken and other meats and as L-arginine in supplements. Arginine is the percursor of nitric oxide, the substance the body uses to maintain a healthy vascular intima. Life-long supplementation with 2 grams arginine twice daily prevents atherosclerosis. Babies born without an enzyme called phosphate synthetase have arginine deficiency syndrome. Adding arginine to their diet permits normal growth and development.
Argyria:  Silver poisoning resulting in ashen gray discolored skin (and other tissues of the body). Due to long-term use of silver salts.
Aristolochia fangchi:  A Chinese herb that is injurious to the kidney and is also associated with an increased risk of cancer of the urinary system. Aristolochia can cause kidney failure requiring renal dialysis or a kidney transplant.
Arm:  In popular usage, the arm extends from the shoulder to the hand. However, in medical terminology, the arm refers to the upper extremity extending from the shoulder only to the elbow. The arm is thus distinguished in medical usage from the forearm which extends from the elbow to the wrist. The arm contains 1 bone: the humerus. (The forearm has 2 bones: the radius and ulna.)
Armed tapeworm:  The pork tapeworm, Taenia solium, a worm contracted from undercooked measly pork (pork infected with the larval forms of the tapeworm). The worm can grow to be 3-6 feet (0.9-1.8 meters) long in the human intestine. The worm is also known as the measly tapeworm. The disease caused by the pork tapeworm is called cysticercosis.
Aromatase:  An enzyme (actually an enzyme complex) involved in the production of estrogen that acts by catalyzing the conversion of testosterone to estradiol. Aromatase is located in estrogen-producing cells in the adrenal glands, ovaries, placenta, testicles, adipose (fat) tissue, and brain. The growth of some breast cancers is promoted by estrogens. Some of the drugs used for breast cancer are aromatase inhibitors which lower the level of estradiol.
Arrectores pilorum (Arrector pili):  Tiny muscles that act as the hair erector muscles. A microscopic band of muscle tissue which connects a hair follicle to the dermis. When stimulated, they contract and cause the hair to become more perpendicular to the skin surface (stand on end).The arrectores pilorum play a key role in goose bumps, a temporary local change in the skin. The chain of events leading to this skin change starts with a stimulus such as cold or fear. That stimulus causes a nerve discharge from the sympathetic nervous system, a portion of the autonomic (involuntary) nervous system. The nerve discharge causes contraction of the arrectores pilorum (the hair erector muscles). Contraction of these muscles elevates the hair follicles above the rest of the skin. And it is these tiny elevations we perceive as goose bumps.
Arrhythmia:  An abnormal heart rhythm. In an arrhythmia the heartbeats may be too slow, too rapid, too irregular, or too early. Rapid arrhythmias (greater than 100 beats per minute) are called tachycardias. Slow arrhythmias (slower than 60 beats per minute) are called bradycardias. Irregular heart rhythms are called fibrillations (as in atrial fibrillation and ventricular fibrillation). When a single heartbeat occurs earlier than normal, it is called a premature contraction.
Arrhythmia, sinus:  The normal increase in heart rate that occurs during inspiration. This is a natural response and is more accentuated in children. The "sinus" refers to the natural pacemaker of the heart which is called the sinoatrial (or sinus) node. It is located in the wall of the right atrium. Normal cardiac impulses start there and are transmitted through specialized cells to the atria and down to the ventricles. Sinus tachycardia refers to a fast heartbeat because of rapid firing of the sinoatrial (sinus) node. This occurs in response to exercise, exertion, excitement, pain, fever, excessive thyroid hormone, low blood oxygen (hypoxia), stimulant drugs (such as caffeine), etc.
Arrhythmias, atrial:  Abnormal heart rhythm due to electrical disturbances in the atria (the upper chambers of the heart) or the AV node (an electrical relay station at the juncture of the atria and ventricles), leading to fast heart beats. Examples of atrial arrhythmias includes atrial fibrillation, atrial flutter, and paroxysmal atrial tachycardia (tremed PAT).
Arrhythmias, rapid:  Abnormally rapid heart rhythms, medically termed tachycardia.
Arrhythmias, slow:  Abnormally slow heart rhythms, medically termed bradycardia.
Arrhythmias, ventricular:  Abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Both are life threatening arrhythmias most commonly associated with heart attack or scarring of the heart muscle from previous heart attack.
Arsenic:  A metallic element that forms a number of poisonous compounds, arsenic is found in nature at low levels mostly in compounds with oxygen, chlorine, and sulfur. These are called inorganic arsenic compounds. Arsenic in plants and animals combines with carbon and hydrogen. This is called organic arsenic. Organic arsenic is usually less harmful than inorganic arsenic. Most arsenic compounds have no smell or special taste. Inorganic arsenic compounds are mainly used to preserve wood. They are also used to make insecticides and weed killers. Copper and lead ores contain small amounts of arsenic. When arsenic enters the environment, it does not evaporate. It gets into air when contaminated materials are burned. It settles from the air to the ground where it does not break down, but can change from one form to another. Most arsenic compounds can dissolve in water. Fish and shellfish build up organic arsenic in their tissues, but most of the arsenic in fish is not toxic. Exposure to arsenic can come from: breathing workplace air with sawdust or burning smoke from wood containing arsenic, ingesting contaminated water, soil, or air at waste sites, ingesting contaminated water, soil, or air near areas naturally high in arsenic. Inorganic arsenic is a human poison. Organic arsenic is less harmful. High levels of inorganic arsenic in food or water can be fatal. A high level is 60 parts of arsenic per million parts of food or water (60 ppm). Arsenic damages many tissues including nerves, stomach and intestines, and skin. Breathing high levels can give you a sore throat and irritated lungs. Lower levels of exposure to inorganic arsenic may cause: nausea, vomiting, and diarrhea, decreased production of red and white blood cells, abnormal heart rhythm, blood vessel damage, a "pins and needles" sensation in hands and feet. Long term exposure to inorganic arsenic may lead to a darkening of the skin and the appearance of small "corns" or "warts" on the palms, soles, and torso. Direct skin contact may cause redness and swelling. Arsenic is a known carcinogen. Breathing inorganic arsenic increases the risk of lung cancer. Ingesting inorganic arsenic increases the risk of skin cancer and tumors of the bladder, kidney, liver, and lung. Tests can measure a person's exposure to high levels of arsenic. Arsenic can be measured in the urine. This is the most reliable test for arsenic exposure. Since arsenic, like other heavy metals, is stored in cells, a "challenge test" with a chelating agent is required to detect high levels. Tests on hair or fingernails can measure exposure to high levels of arsenic over the past 6-12 months, however these tests are not useful for quantitative measurements of body burden. Arsenic has, historically, been a favorite form of murder. For example, Napoleon was murdered by his cook who placed a small amount of arsenic in Napoleon'a food at each meal for several months.
ART (antiretroviral therapy):  Treatment that suppresses or stops a retrovirus. One of the retrovirus is the human immunodeficiency virus (HIV) that, along with many other factors, is associated with AIDS.
Arterial aneurysm:  An outpouching (aneurysm) of an artery. As opposed to a venous or cardiac aneurysm. An aneurysm is a localized widening (dilatation) of an artery, vein, or the heart. At the area of an aneurysm, there is typically a bulge and the wall is weakened and may rupture. The word "aneurysm" comes from the Greek aneurysma meaning "a widening."
Arterial blood gases (ABG):  The sampling of the blood levels of oxygen and carbon dioxide within the arteries, as opposed to the levels of oxygen and carbon dioxide in venous blood. Typically the acidity, or pH, of the blood is measured simultaneously with the gas levels in ABG sampling. Blood gas is reported as pO2 and pCO2.
Arterial tension:  The pressure of the blood within an artery, the arterial pressure. Also called the intra-arterial pressure.
Arteriogram:  An x-ray of blood vessels, which becomes visible after an injection of contrast solution into the circulation that appears on the x-ray film. Frequently used to evaluate suspected vascular heart disease. An invasive and non-benign procedure. Mortality rates up to 1%. Studies have shown that the "percentage blockage" reported by doctors who read arteriograms is not a reproducible result, i.e. it is a gross estimate which be off by 50% or more.
Arteriole:  A small branch of an artery (a vessel that carries blood high in oxygen away from the heart to the body) leading to a capillary. The oxygenated hemoglobin (oxyhemoglobin) makes the blood in arteries and arterioles look bright red.
Arteriosclerosis:  Hardening and thickening of the walls of the arteries that occurs universally with age due to diffuse depositoin of calcium in the muscle and connective tissue of the arteries and arterioles. Frequently confused, even by doctors, with atherosclerosis (which involves plaque formation). Associated with elevated blood pressure due to the fact that a calcified arterial system cannot expand and contract with each heart beat and therefore cannot absorb the shock of pressure generated by the heart beat. Hardening of the arteries is part of the generalized phenomenon of calcium depositon with age which happens throughout the body leading to many of the changes seen with aging. This condition is treatable with intravenous EDTA chelation therapy which returns flexibility to the entire system, including the vascular system.
Arteriovenous malformation (AVM):  is a congenital disorder of blood vessels in the brain, brainstem, or spinal cord that is characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications). Fistulas in the AVM permit shunting of blood from the arterial to the venous side of the circulation without passage through a capillary system. This shunting causes low blood pressure (hypotension) in the arterial vessels feeding the AVM and neighboring areas of the brain that they normally supply with blood. AVMs typically cause problems before the age of 40. The most common symptoms of AVM include hemorrhaging (bleeding), seizures, headaches, and neurological problems such as paralysis or loss of speech, memory, or vision. The frequency of hemorrhage in various series ranges from 30-82%. AVM rupture accounts for 2% of all strokes and in death in about 50% of cases.
Arteritis, cranial:  A serious disease characterized by inflammation of the walls of the blood vessels (vasculitis). The age of affected patients is usually over 50. Cranial arteritis is also known as temporal arteritis and as giant cell arteritis. It can lead to blindness and/or stroke. The disease is detected by a biopsy of an artery. It is treated with high dose cortisone-related medications.
Artery:  A vessel that carries blood high in oxygen content away from the heart to the farthest reaches of the body. Since blood in arteries is usually full of oxygen, the hemoglobin in the red blood cells is oxygenated. The resultant form of hemoglobin (oxyhemoglobin) is what makes arterial blood look bright red.
Arthralgia:  Joint pain
Arthritis:  Inflammation of a joint.
Arthrocentesis:  Joint aspiration, a procedure whereby a sterile needle and syringe are used to drain fluid from a joint. This is usually done as an office procedure or at the bedside in the hospital. Joint fluid is typically sent for examination to the lab to determine the cause of the joint swelling, such as infection, gout, and rheumatoid arthritis. Arthrocentesis can be helpful in relieving joint swelling and pain. Occasionally, cortisone medications are injected into the joint during the arthrocentesis in order to rapidly relieve joint inflammation and further reduce symptoms.
Arthrogryposis:  Joint contractures that develop before birth and are evident at birth. A newborn with arthrogryposis lacks the normal range of motion in one or more joints. Prenatal limitation of joint mobility can result from: (1) neurologic deficits including anencephaly, defects of the spine such as spina bifida, and nerve deficiencies, (2) muscle deficits including failure of muscle development, fetal diseases of muscle, myotonic dystrophy, and myasthenia gravis, (3) connective tissue and skeletal defects including fusion of bones (synostosis), failure of a joint to develop, prenatal fixation of a joint, excess laxity and of dislocation of joints, and fixation of soft tissue around the joint, (4) fetal crowding or constraint (fetal constraint occurs from lack of amniotic fluid (oligohydramnios) due to underproduction of fluid by the fetal kidneys, failure to swallow and recirculate the fluid, or chronic leakage of fluid.
Arthrogryposis multiplex congenita (AMC):  A disorder that develops before birth, present at birth, and characterized by reduced mobility of multiple joints. In AMC the range of motion of the joints in the arms and legs is usually limited or fixed. Joints affected may include the shoulders, elbows, wrists and fingers and the hips, knees, ankles, and feet - virtually any and all joints. The impairment of joint mobility is often accompanied by overgrowth (proliferation) of fibrous tissue in the joints (fibrous ankylosis).
Arthroscopy:  Refers to a surgical technique whereby a doctor inserts a tube-like instrument into a joint to inspect, diagnose and repair tissues. It is most commonly performed in patients with diseases of the knees or shoulders. The word arthroscopic is often confused with orthoscopic. Orthoscopic means having correct vision or producing it.
Arthrosis:  Another word for joint.
Articulation:  As regards the skeleton, another word for joint.
Articulation disorder:  The inability to correctly produce speech sounds (phonemes) because of the imprecise placement, timing, pressure, speed, or flow of movement of the lips, tongue, or throat.
Artificial abortion:  An abortion that is brought about intentionally. Also called an induced or therapeutic abortion. As opposed to a spontaneous abortion (a miscarriage).
Artificial heart:  A manmade heart. An artificial heart was temporarily implanted in 1969 by Denton Cooley in Houston, Texas. Complete replacement of the heart by an artificial heart was done in 1982 by William DeVries at Salt Lake City, Utah. Dentist Barney Clark was the patient. Clark died soon thereafter.
Artificial insemination:  A procedure in which a fine catheter (tube) is inserted through the cervix (the natural opening of the uterus) into the uterus (the womb) to deposit a sperm sample directly into the uterus. The purpose of this relatively simple procedure is to achieve fertilization and pregnancy. Artificial insemination is also called intrauterine insemination (IUI).
Artificial knee:  A replacement for the human knee. An artificial knee typically has a metal shell on the end of the thigh bone (the femur), a metal and plastic trough on the shin bone (the tibia), and sometimes a plastic button in the kneecap (the patella). An artificial knee is exchanged for the human knee by a surgical procedure known as total knee replacement. The artificial parts are cemented into place. Knee replacement is done on people, usually over 55, whose knees have been so damaged by arthritis, trauma, or other destructive diseases of the joint that they have severe pain, stiffness, instability or deformity (lock-knees or bowlegs) of the knee. The most common reason for knee replacement is osteoarthritis. An artificial knee is not a normal knee nor is it as good as a normal knee. The main long-term problem is loosening which occurs because the cement crumbles or the bone.
Artificial pacemaker:  A device that uses electrical impulses to regulate the heart rhythm or to reproduce that rhythm. An internal pacemaker is one in which the electrodes into the heart, the electronic circuitry and the power supply are implanted (internally) within the body. Although there are different types of pacemakers, all are designed to treat bradycardia, a heart rate that is too slow. Pacemakers may function continuously and stimulate the heart at a fixed rate or at an increased rate during exercise. A pacemaker can also be programmed to detect too long a pause between heartbeats and then stimulate the heart. The internal pacemaker was invented by Wilson Greatbatch in 1958.
ASA:  Abbreviation for acetylsalicylic acid (aspirin).
Asbestosis:  A condition featuring scarring of the lungs caused by inhaled asbestos fibers. Asbestosis is irreversible. It tends to lead to COPD (chronic obstructive pulmonary disease), a progressive disorder that can be disabling or fatal. When asbestos fibers lodge in the lungs and penetrate through the intestinal tract, they can also lead to lung cancer or to mesothelioma, a cancer of the mesothelium, the thin lining on the surface of the body cavities and the organs that are contained within them.
Ascariasis:  Infection with Ascaris lubricoides, the intestinal roundworm, the most common worm infection in humans. Ascaris eggs are found in the soil. Infection occurs when a person accidently ingests (swallows) infective ascaris eggs. Once in the stomach, larvae (immature worms) hatch from the eggs, penetrate the intestinal wall and are carried to the lungs then where they leave the circulation and enter the air passages passing upward to the throat where they are then swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms can grow over 12 inches (4.8 cm) in length. Adult male worms are smaller. Adult female worms lay eggs that are then passed in feces; this cycle takes between 2 and 3 months. Adult worms can live 1 to 2 years. Infection occurs worldwide. It is most common in tropical and subtropical areas where sanitation and hygiene are poor. Children are infected more often than adults. In the US, infection is not common and occurs mostly in rural areas of the southeast. Pigs can be infected with ascaris. Occasionally, a pig infection can be spread to humans.
Ascending aorta:  The ascending aorta is the first section of the aorta, the largest artery in the body. The ascending aorta starts from the left ventricle of the heart and extends to the arch (the bend) of the aorta. The right and left coronary arteries that supply blood to the heart muscle arise from the ascending aorta.
Ascites:  Abnormal buildup of fluid in the abdomen. Ascites can occur as a result of severe liver disease.
Ascorbic acid:  Vitamin C, an essential nutrient found mainly in fruits and vegetables. The body requires it to form and maintain bones, blood vessels, and skin. Like other vitamins, ascorbic acid is an organic compound. Ascorbic acid is a water-soluble vitamin, one that cannot be stored by the body except in insignificant amounts. It must be replenished daily. Ascorbic acid helps produce collagen, a protein needed to develop and maintain healthy teeth, bones, gums, cartilage, vertebrae discs, joint linings, skin and blood vessels. Ascorbic acid also does the following:
  1. Promotes the healing of cuts, abrasions and wounds.
  2. Helps fight infections.
  3. Inhibits conversion of irritants in smog, tobacco smoke, and certain foods into cancer-causing substances.
  4. Appears to dilate (widen, enlarge) blood vessels and thereby lessen the risk of developing high blood pressure and heart disease.
  5. Helps regulate cholesterol levels.
  6. Prevents the development of scurvy, a disease characterized by weakness, fatigue, anemia, swollen joints, bleeding gums and loose teeth. Scurvy was common aboard ships in earlier times because crews traveled for long periods without eating fresh vegetables or fruit. Many sailors died of the disease. Scurvy is rare today.
  7. Appears to lower the risk of developing cataracts, clouding of the lens of the eye that impairs vision.
  8. May help protect diabetics against deterioration of nerves, eyes and kidneys.
  9. Inhibits the development of colds and decrease the intensity of cold symptoms (in high doses of the ascorbate form.)
  10. Aids iron absorption.
  11. May reduce levels of lead in the blood.
Ascus:  An elongated spore case containing the spores of certain fungi including yeast.
ASD:  Acronym for atrial septal defect.
Aseptic:  The absence of microorganisms. By contrast, something that just discourages the growth of microorganisms is antiseptic.
Aseptic necrosis:  Condition in which poor blood supply to an area of bone leads to bone death. Also called avascular necrosis and osteonecrosis.
Asian cholera:  A devastating and sometimes lethal disease with intense vomiting and profuse watery diarrhea was discovered in 1883 to be due to infection with the bacteria Vibrio cholerae, a discovery made by the renowned German bacteriologist Robert Koch (1843-1910). Asian cholera is synonymous with cholera.
Asparagine:  An amino acid, one of the 20 building blocks of protein. Asparagine is nonessential to the diet since the body can synthesize it. Asparagine is important to the metabolism of ammonia. It was the first amino acid to be isolated from a natural source, asparagus juice (1806).
Aspartame:  A man-made sweetener with almost no calories used in place of sugar. Aspartame is a compound of two amino acids - aspartic acid and phenylalanine. Because it is essentially half phenylalanine, people who have the genetic disease phenylketonuria (PKU) and cannot metabolize phenylalanine normally need to avoid diet drinks and other products containing aspartame (trade name: NutraSweet). That is the party line. Beyond that, many doctors (including this writer) and member of the public believe that the breakdown products of aspartame are toxic and can lead to mis-behavior syndromes in children and illness in people of all ages. See:
Aspartate aminotransferase (AST):  Also known as serum glutamic oxaloacetic transaminase (SGOT), AST is an enzyme that is normally present in liver and heart cells. AST is released into blood when the liver or heart is damaged. The blood AST levels are thus elevated with liver damage (for example, from viral hepatitis) or with an insult to the heart (for example, from a heart attack). Some medications can also raise AST levels by breaking down liver or heart cells and releasing the enzyme.
Aspartic acid:  An amino acid, one of the 20 building blocks of protein. A amino acid that is not essential to the human diet, aspartic acid was discovered in protein in 1868. It has a role as a neurotransmitter.
Asperger syndrome:  A pervasive developmental disorder characterized by an inability to understand how to interact socially. Other typical features of the syndrome include clumsy and uncoordinated motor movements, social impairment with extreme egocentricity, limited interests and/or unusual preoccupations, repetitive routines or rituals, speech and language peculiarities, and non-verbal communication problems. Children with Asperger syndrome generally have few facial expressions apart from anger or misery. Most have excellent rote memory and musical ability, and become intensely interested in one or two subjects (sometimes to the exclusion of other topics). They may talk at length about a favorite subject or repeat a word or phrase many times. Children with Asperger syndrome tend to be "in their own world" and preoccupied with their own agenda. The onset of Asperger syndrome commonly occurs after the age of 3.
Aspergillosis:  Infection with the fungus Aspergillus, seen especially in people with a deficient immune system. The clinical features of aspergillosis can include invasive lung infection and disseminated disease, usually with fever, cough, spitting up blood, and chest pain. Aspergillosis may mimic asthma with cough and inspiratory stridor (noise on breathing in) or sinusitis with fever, localized pain.
Aspergillus:  A family of fungal organisms and molds, some of which can cause disease (aspergillosis).
Asphyxia:  a lack of oxygen or excess of carbon dioxide in the body that is usually caused by interruption of breathing and that causes unconsciousness.
Aspirate:  To suck in.
Aspiration:  Removal of a sample of fluid and cells through a needle. Aspiration also refers to the accidental sucking in of food particles or fluids into the lungs.
Aspiration pneumonia:  Infection of the lungs due to aspiration (the sucking in of food particles or fluids into the lungs).
Aspirin:  Once the Bayer trademark for acetylsalicylic acid (ASA). The first use of what became known as aspirin was by the Greek physician Hippocrates, who used powder extracted from the bark of a willow tree to treat pain and reduce fever. The bark contained salicin, a component of acetylsalicylic acid. Salicin was successfully isolated from willow bark in 1829 but it often irritated the stomach. Two years after a young Bayer researcher, Felix Hoffman, synthesized acetylsalicylic acid, Bayer registered the trademark "aspirin" on March 6, 1899.
Asplenia:  The absence of a spleen or the presence of a spleen that functions does not function. (The spleen can be functionally destroyed, as occurs in patients with sickle cell disease.)
Assay:  An assay is an analysis done to determine the presence of a substance and the amount of that substance. Thus, an assay may be done for example to determine the level of thyroid hormones in the blood of a person suspected of being hypothyroid (or hyperthyroid). The term is also used to denote the determination of biological or pharmacological potency of a drug. For example, an assay may be done of a vaccine to determine its potency.
Assisted living:  A type of long-term care facility for elderly or disabled people who are able to get around on their own but who may need help with some activities of daily living, or simply prefer the convenience of having their meals in a central cafeteria and having nursing staff on call.
Assisted suicide:  The deliberate hastening of death by a terminally ill patient with assistance from a doctor, family member, or another individual.
AST:  Aspartate aminotransferase, an enzyme normally present in liver and heart cells. AST is released into blood when the liver or heart is damaged. The blood AST levels are thus elevated with liver damage (for example, from viral hepatitis) or with an insult to the heart (for example, from a heart attack). Some medications can also raise AST levels. AST is also known as serum glutamic oxaloacetic transaminase (SGOT).
astasia:  The inability to stand in a normal manner.
astasia-abasia:  The inability to either stand or walk in a normal manner; the gait is bizarre and is not suggestive of an organic lesion; often the patient sways wildly and nearly falls, recovering at the last moment; a symptom of hysterical conversion reaction. (hysteria A nervous affection in which the emotional and reflex excitability is exaggerated, and the will power correspondingly diminished, so that the patient loses control over the emotions, becomes the victim of imaginary sensations, and often falls into paroxysms or fits. The chief symptoms are convulsive, tossing movements of the limbs and head, uncontrollable crying and laughing, and a choking sensation as if a ball were lodged in the throat. The affection presents the most varied symptoms, often simulating those of the gravest diseases, but generally curable by mental treatment alone.) (conversion An unconscious defense mechanism by which the anxiety that stems from intrapsychic conflict is converted and expressed in one or more symbolic somatic symptoms.)
Asthma:  A common disorder in which chronic inflammation of the bronchial tubes (bronchi) makes them swell, narrowing the airways. Asthma involves only the bronchial tubes and does not affect the air sacs (alveoli) or the lung tissue (the parenchyma of the lung) itself. Airway narrowing in asthma is due to three major processes acting on the bronchi: inflammation (see above), spasm (bronchospasm), and hyperreactivity (over-reaction of the bronchi to factors that can precipitate asthma). The incidence of asthma has risen dramatically in the past 20 years.
Astigmatism:  A common form of visual impairment in which part of an image is blurred, due to an irregularity in the curvature of the front surface of the eye, the cornea. The curve of the cornea is shaped more like a spoon than a sphere. Light rays entering the eye there are not uniformly focused on the retina.
Astraphobia:  An abnormal and persistent fear of thunderstorms. Sufferers experience anxiety even when they realize the risk of harm is very small. Consequently, when indoors they might seek shelter under a bed, in a closet or in a basement. They generally keep a watchful eye on the sky and remain alert for reports of electrical storms. "Astraphobia" is derived from the Greek "aster" (star) and "phobos" (fear). A related term is brontophobia: fear of thunder.
Astrocytoma:  A tumor that begins in the brain or spinal cord in small, star-shaped cells called astrocytes. The location of the tumor depends on the age of the person. In adults, astrocytomas most often arise in the cerebrum whereas in children, they may arise in the brain stem, cerebrum, and cerebellum. Astrocytomas are gliomas, brain tumors derived from glial, or supportive, cells. A far advanced (grade IV) astrocytoma is usually called a glioblastoma multiforme.
Asymptomatic:  Without symptoms.
Ataxia:  Incoordination and unsteadiness due to the brain’s failure to regulate the body’s posture and regulate the strength and direction of limb movements. Ataxia is usually a consequence of disease in the brain, specifically in the cerebellum which lies beneath the back part of the cerebrum.
Atelectasis:  Failure of full expansion of the lung at birth (primary atelectasis) or a collapse thereafter (secondary atelectasis).
ATG:  Antithymocyte globulin.
Athelia:  Absence of the nipple.
Atherectomy:  A procedure for opening up an artery by removing the plaque (atheroma) produced by the build-up of cholesterol and other fatty substances in the inner lining of the artery from atherosclerosis. Atherectomy is done most often in major arteries - such as the coronary arteries within the heart muscle and the carotid and vertebral arteries leading up to the head and brain - that have experienced the occlusive effects of atherosclerosis.
Atherogenesis:  The process of forming atheromas, plaques in the inner lining (the intima) of arteries. This condition is completely avoidable by nutritional means but nevertheless takes the lives of 2/3 of the American population.
Atherosclerosis:  the formation of plaques in the wall of arteries.
Athetosis:  Involuntary writhing movements particularly of the arms and hands.
Athlete foot:  A skin infection caused by a fungus called Trichophyton which can thrive and infect the upper layer of the skin when the feet (or other areas of the body) remain moist, warm, and irritated. The fungus can be found on floors and in socks and clothing and can be spread from person to person by contact with these objects. However, without proper growing conditions (a warm, moist acidic environment), the fungus will not infect the skin.
Atkins diet:  A high-protein, high-fat, low-carbohydrate weight-loss diet popularized by Dr. Robert C. Atkins that allows for unrestricted amounts of meat, cheese and eggs while severely restricting carbohydrates, including sugar, bread, pasta, milk, fruits and vegetables. The Atkins diet is based on the theory that eating carbohydrates stimulates the production of insulin, which in turn leads to hunger, eating, and weight gain. The theory is that people on the Atkins diet experience reduced appetite and their bodies use stored fat for energy versus burning glucose from ingested carbohydrate. Burning fat for energy is supposedly lead to weight loss.
Atlantoaxial:  Pertaining to the first and second cervical vertebrae which meet at a joint called the atlantoaxial joint. The uppermost cervical vertebra (the atlas) rotates about the odontoid process of the second cervical vertebra (the axis). The joint between the axis and atlas is a pivot type of joint that allows the head turn.
Atlas and axis joint:  The joint between the atlas and axis bones. The atlas is the first cervical (neck) vertebra which is just under the head; it is named for Atlas, the Greek god who supported the world on his shoulders. The axis is the second cervical vertebra; it has what is called the odontoid process about which the atlas rotates. The joint between the atlas and axis is a pivot type of joint. It allows the head turn from side to side. It is also called the atloaxoid joint. The ligaments that serve to support and strengthen this joint are called the capsular; anterior and posterior atlantoaxial; and transverse ligaments. They are important structures to be strengthened in prolotherapy when weakness due to degenerative disease of the neck is repaired.
Atlas: The atlas is the first cervical (neck) vertebra (symbol C1). It supports the head. The atlas bone is named for the Greek god Atlas who wa:  
Atom:  The smallest part of any material that cannot be broken up by chemical means. Each atom has a center (the nucleus) which contains protons and neutrons. Electrons orbit around the nucleus. The atom is primarily empty space. To put it in proportions, if the nucleus of an atom were the size of the button on a baseball pitcher's cap, the electrons would be like dust particles revolving around the outside of the baseball stadium.
Atonia in REM sleep:  A frightening form of paralysis that occurs when a person suddenly finds himself or herself unable to move for a few minutes, most often upon falling asleep or waking up. Commonly called sleep paralysis, the condition is due to an ill-timed disconnection between the brain and the body. The symptoms of sleep paralysis include sensations of noises, smells, levitation, paralysis, terror, and images of frightening intruders. Once considered very rare, about half of all people are now believed to experience sleep paralysis sometime during their life. Sleep paralysis strikes as a person is moving into or out of REM (rapid eye movement) sleep, the deepest part of sleep.
Atopic:  Prone to allergies or characterized by allergy.
Atopic dermatitis:  A skin disease characterized by areas of severe itching, redness, scaling, and loss of the surface of the skin (excoriation). When the eruption (rash) has been present for a prolonged time, chronic changes occur due to the constant scratching and rubbing known as lichenification (thickening of the skin with accentuation of the skin lines to form a crisscross pattern). Atopic dermatitis is the most common of the many types of eczema. This disorder usually affects young children on the face and extensor surfaces of the arms and legs (elbow and knee sides). Older children and adults are usually affected on the sides of the neck and on the inside of the elbow and knee. Atopic dermatitis is frequently associated with other atopic (allergic) disorders, especially asthma and allergic rhinitis (hayfever). A defect of the immune system within the skin has been shown, but the reason for this is unknown.
ATP (acute thrombocytopenic purpura):  Sudden onset of low blood platelet levels with bleeding into the skin and elsewhere. ATP is due to many causes. It may, for example, constitute a potentially serious complication during the acute phase of measles. More commonly it is a medication side-effect.
ATP (adenosine triphosphate):  A compound of critical importance in the storage of energy within cells in the body and in the synthesis (the making) of RNA. ATP is a nucleotide (a building block of a nucleic acid such as RNA). The body produces ATP from food and then ATP produces energy as needed by the body.
Atresia:  Absence of a normal opening or failure of a structure to be tubular. Atresia can affect many structures in the body, including
  • Anal atresia - congenital absence of a hole at the bottom end of the intestine. Also called imperforate anus.
  • Aortic atresia - congenital absence of the normal valvular opening into the aorta.
  • Biliary atresia - absence of the major bile ducts, causing jaundice.
  • Choanal atresia - congenital failure of one or both nasal passages to open.
  • Esophageal atresia - a birth defect in which part of esophagus is not hollow.
  • Intestinal atresia - obliteration of the hollow of the small intestine, involving the ileum (50% of cases) or the jejunum or duodenum.
  • Laryngeal atresia - congenital failure of the laryngeal opening to develop, resulting in partial or total obstruction at or just above or below the glottis.
  • Pulmonary atresia - congenital absence of the pulmonary valve opening in the heart.
  • Tricuspid atresia - congenital lack of the tricuspid valve opening.
  • Vaginal atresia - congenital occlusion of the vagina or subsequence adhesion (sticking together) of the walls of the vagina occluding it.
Atria:  The plural of atrium. The atria are the two smaller chambers of the heart. The right atrium receives blood from the body and the left atrium receives blood from the lungs.
Atrial septal defect (ASD):  A hole in the septum, the wall, between the atria, the upper chambers of the heart. Commonly called an ASD. ASDs constitute a major class of heart formation abnormalities present at birth (congenital cardiac malformations). Normally, when clots in veins break off, they travel first to the right side of the heart and, then to the lungs where they lodge as an obstruction (embolus). The lungs act as a filter to prevent the clots from entering the arterial circulation. However, when there is an ASD, a clot can cross from the right to the left side of the heart (bypassing the lungs), then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident). Because of the risk of stroke from paradoxical embolism, it is usually recommended that even small ASDs be surgically repaired.
Atrial septum:  The wall between the two upper chambers (the right and left atrium) of the heart.
Atrioventricular node:  The atrioventricular (AV) node is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles. The AV node is one of the major elements in the cardiac conduction system, the system that controls the heart rate.
Atrium:  One of the two smaller chambers of the heart. Each atrium consists of an open space with recessed walls. (The plural of atrium is atria.) The right atrium receives deoxygenated blood from the body through the vena cava and pumps it into the right ventricle which then sends it to the lungs. The left atrium receives oxygenated blood back from the lungs and pumps it down into the left ventricle for relatively high-pressure delivery to the body. The atrium was an open area in the center of an ancient Roman home. The atria of the heart are also called the auricles (the Latin auricula means little ear) because they resemble the floppy ears of a dog.
Atrophic vaginitis:  Thinning of the lining (the endothelium) of the vagina due to decreased production of estrogen. This may occur with menopause. Vaginitis means inflammation of the vagina, the muscular canal extending from the cervix to the outside of the body. Aside from atrophic vaginitis, there are a number of other types of vaginitis. Vaginitis may, for example, be caused by a fungal infection leading to itching or burning and a discharge.
Atrophy:  Wasting away or diminution. Muscle atrophy is wasting of muscle, decrease in muscle mass. A nerve can also show atrophy. For example, atrophy of the optic nerve diminishes vision.
Atropine:  A drug obtained from belladonna that is administered via injection, eye drops, or in oral form to relax muscles by inhibiting nerve responses. Used to dilate the pupils and as an antispasmodic.
Atropine psychosis:  A syndrome characterized by dry mouth, blurred vision, forgetfulness, and difficulty with urination triggered by atropine and the anticholinergic effects of other drugs, particularly anti-psychotic medications. Treatment is to reduce or stop the medication.
Attention deficit disorder (ADD):  An inability to control behavior due to difficulty in processing neural stimuli.
Attention deficit hyperactivity disorder:  A family of related chronic neurobiological disorders that interfere with an individual's capacity to regulate activity level (hyperactivity), inhibit behavior (impulsivity), and attend to tasks (inattention) in developmentally appropriate ways. The term "attention deficit hyperactivity disorder" is abbreviated and usually referred to as ADHD. The core symptoms of ADHD include an inability to sustain attention and concentration, developmentally inappropriate levels of activity, distractibility, and impulsivity. There is a strong suspician that the extraordinary intake of simple sugar found in present day America is behind the radical increase in incidence of this syndrome.
Attenuate:  To weaken, dilute, thin, reduce, weaken, diminish. In medicine "attenuate" refers to procedures that weaken an agent of disease (a pathogen). An attenuated virus is a weakened, less vigorous virus. A vaccine against a viral disease can be made from an attenuated, less virulent strain of the virus, a virus capable of stimulating an immune response and creating immunity but not causing illness.
Atypical:  Not typical, not usual, not normal, abnormal. Atypical is often used to refer to the appearance of precancerous or cancerous cells.
Atypical measles syndrome (AMS):  An altered expression of measles, AMS begins suddenly with high fever, headache, cough, and abdominal pain. The rash may appear 1 to 2 days later, often beginning on the limbs. Swelling (edema) of the hands and feet may occur. Pneumonia is common and may persist for 3 months or more. AMS occurs in persons who were incompletely immunized against measle. This may happen if a person were given the old killed-virus measles vaccine (which does not provide complete immunity and is no longer available); or the person were given attenuated (weakened) live measles vaccine that was, by accident, inactivated during improper storage. Immunization with inactivated measles virus does not prevent measles virus infection. It can, however, sensitize a person so that the expression of the disease is altered, resulting in AMS. Being atypical, AMS can be confused with other entities including Rocky Mountain spotted fever, meningococcal infection, various types of pneumonia, appendicitis, juvenile rheumatoid arthritis, etc.
Audiogram:  A test of hearing at a range of sound frequencies.
Audiologist:  A health care professional who is trained to evaluate hearing loss and related disorders, including balance (vestibular) disorders and tinnitus (ringing in the ears) and to rehabilitate individuals with hearing loss and related disorders.
Audiology:  The study of hearing.
Audiometry:  The measurement of hearing.
Auditory acuity:  The clarity or clearness of hearing, a measure of how well a person hears. Auditory acuity is what is measured when determining the need for a hearing aide and monitoring the ability to hear.
Auditory cortex:  The part of the brain that is concerned with hearing. The auditory cortex is the temporal lobe, which is the lower lobe of the cerebral hemisphere just forward of the occipital lobe.
Auditory tube:  The tube that runs from the middle ear to the pharynx, also known as the Eustachian tube. The function of this tube is to protect, aerate and drain the middle ear (and mastoid). Occlusion of the Eustachian tube leads to the development of middle ear inflammation (otitis media).
Aura:  A premonition. There is often an aura before a migraine or a grand mal seizure. The aura, a symptom of brain malfunction, may consist of flashing lights, a gleam of light, blurred vision, an odor, the feeling of a breeze, numbness, weakness, or difficulty speaking.
Auricle:  The ear (actually, the pinna which is the principal projecting part of the ear) or something that is ear shaped like the upper chamber (atrium) of the heart.
Auscultate:  To listen to the sounds made by the internal organs of the body for diagnostic purposes. For example, nurses and doctors auscultate the lungs and heart of a patient by using a stethoscope placed on the patient's chest.
Autism:  A spectrum of neuropsychiatric disorders characterized by deficits in social interaction and communication, and unusual and repetitive behavior. Some, but not all, people with autism are non-verbal.
Autoantibody:  An antibody directed against the patient's own body tissue. This occurs in the so-called autoimmue or collagen vascular disorders.
Autoclave:  A chamber for sterilizing with steam under pressure. The original autoclave was essentially a pressure cooker. The steam tightened the lid. The device was called an autoclave (from the Greek auto, self + clavis, key) meaning self-locking.
Autocrine:  A hormone or chemical messenger (called the autocrine agent) secreted by a cell that binds to autocrine receptors on the same cell, leading to changes in the cell. This is a case of a cell signaling itself.
Autogenous:  Self-produced.
Autoimmune:  Pertaining to autoimmunity, a misdirected immune response that occurs when the immune system goes awry and attacks the body itself. Autoimmunity is present to some extent in everyone and is usually harmless. However, autoimmunity can cause a broad range of human illnesses, known collectively as autoimmune diseases. Autoimmune diseases occur when there is progression from benign autoimmunity to pathogenic autoimmunity. Autoimmunity is evidenced by the presence of autoantibodies (antibodies directed against the person who produced them) and T cells that are reactive with host antigens.
Autoimmune disease:  An illness that occurs when the body tissues are attacked by its own immune system.
Autoimmune lymphoproliferative syndrome (ALPS):  A disease caused by failure of lymphocytes to die once they have finished doing their job. As a result, lymphocytes persist in the spleen and lymph nodes which grow large, and immune cells attack the body's own tissues, a condition known as autoimmunity.
Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED):  A genetic autoimmune disease with an extraordinary array of clinical features but characterized most often by at least 2 of the following 3 findings: hypoparathyroidism - underfunction of the parathyroid glands which control calcium, candidiasis (yeast infection), and adrenal insufficiency (underfunction of the adrenal gland). APECED was the first systemic (bodywide) autoimmune disease found due to a defect in a single gene.
Autoimmune thyroid disease:  Disease of the thyroid gland due to autoimmunity in which the patient's immune system attacks and damages their thyroid. Graves disease and Hashimoto's thyroiditis are forms of autoimmune thyroid disease. In these diseases, thyroid-reactive T cells are formed that infiltrate the thyroid gland. Both disorders are common with a prevalence of about 1% in the US.
Autoimmune thyroiditis:  Hashimotos's disease.
Autologous:  In blood transfusion and transplantation, a situation in which the donor and recipient are the same person. Patients scheduled for non-emergency surgery may be autologous donors by donating blood for themselves that will be stored until the surgery. An autologous graft is providing a graft, for example of skin, to yourself.
Autolysis:  The enzymatic digestion of cells by enzymes present within them. The cells most susceptible to autolysis tend to be dying or dead cells in both plants and animals. In cooked food these enzymes are destroyed placing a heavier burden on the pancreas to produce enzymes for digestion.
Automated external defibrillator:  A device that automatically analyzes the heart rhythm and, if it detects a problem that may respond to an electrical shock, that permits a shock to be delivered to restore a normal heart rhythm. Abbreviated AED. Thanks to their small size and ease of use, AEDs have been installed in many settings (such as schools and airports) and serve a role in expanding the number of opportunities for life-saving defibrillation.
Automated white cell differential:  A machine-generated percentage of the different types of white blood cells, usually split into granulocytes, lymphocytes, monocytes, eosinophils, and basophils. This bypasses the human element in analysis and fails to made fine distinctions which can be made by a trained human.
Automatic behavior:  A behavior that is performed without conscious knowledge and that does not appear to be under conscious control. Automatic behavior involves doing something "automatically" and not remembering afterwards how one did it or even that one did it. Automatic behavior is also called automatism.
Autonomic nervous system:  Part of the nervous system that was once thought to be functionally independent of the brain. The autonomic nervous system regulates key functions of the body including the activity of the heart muscle (see below), the smooth muscles (e.g., the muscles of the intestinal tract), and the glands. The autonomic nervous system has two divisions: (1) the sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure; and (2) the parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles.
Autonomic neuropathy:  Disease of the nerves affecting mostly the internal organs such as the bladder muscles, the cardiovascular system, the digestive tract, and the genital organs. These nerves are not under a person's conscious control and function automatically (autonomically). Autonomic neuropathy can be associated with diabetes, alcohol abuse, nerve injury and the use of certain medications. The symptoms depend upon what organs are affected and may include abdominal swelling, heat intolerance, nausea, vomiting, impotence, diarrhea, constipation, dizziness with standing, difficulty urinating and urinary incontinence. Autonomic neuropathy is also called visceral neuropathy because it affects the viscera (the internal organs).
Autophobia:  An abnormal and persistent fear of loneliness, of being alone. A fear of solitude. Sufferers from autophobia may experience anxiety even though they realize that being alone does not threaten their well-being. They may worry about being ignored and unloved, or they may worry about intruders, strange noises or the possibility of developing a medical problem. Autophobia also has another sense, that of an irrational fear of oneself, intense self-fear that s groundless. Then there is another meaning - fear of automobiles (just kidding).
Autopsy:  A postmortem (after death) anatomical and (sometimes) microscopic examination. Also called a necropsy. An autopsy is used to determine cause of deathand to reveal any hidden conditions the person may have had.
Autosomal chromosome:  Any chromosome except for the sex chromosomes. Humans have 44 autosomal chromosomes, or autosomes and two sex chromosomes.
Autosomal dominant:  A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes. Individuals with autosomal dominant diseases have a 50-50 chance of passing the mutant gene and therefore the disorder onto each of their children. Examples of autosomal dominant diseases include Huntington disease, neurofibromatosis, and polycystic kidney disease.
Autosomal recessive:  A genetic condition that appears only in individuals who have received two copies of an autosomal gene, one copy from each parent. The gene is on an autosome, a nonsex chromosome. The parents are carriers who have only one copy of the gene and do not exhibit the trait because the gene is recessive to its normal counterpart gene. If both parents are carriers, there is a 25% chance of a child inheriting both abnormal genes and, consequently, developing the disease. There is a 50% chance of a child inheriting only one abnormal gene and of being a carrier, like the parents, and there is a 25% chance of the child inheriting both normal genes.
AV (atrioventricular):  AV is the standard medical abbreviation for atrioventricular, a combination that means pertaining to the atria (the upper chambers of the heart) and the ventricles (the lower chambers of the heart).
AV node:  The AV node (AV stands for atrioventricular) is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles.
Avascular necrosis:  Condition in which poor blood supply to an area of bone leads to bone death. Also called and osteonecrosis.
Avian Influenza:  Also called fowl plague, avian flu, and bird flu. A highly contagious viral disease with up to 100% mortality in domestic fowl. Caused by influenza A virus subtypes H5 and H7. All types of birds are susceptible to the virus but outbreaks occur most often in chickens and turkeys. The infection may be brought by migratory wild birds which can carry the virus but show no signs of disease. Humans are only rarely affected.
Avian Tuberculosis:  A type of tuberculosis affecting birds, caused by Mycobacterium avium, which may be communicated to other animals and humans.
AVM (arteriovenous malformation):  is a congenital disorder (one present at birth) of blood vessels in the brain, brainstem, or spinal cord that is characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications).
Avulsion:  Tearing away. A nerve can be avulsed by an injury, as can skin or even part of a bone.
Axilla:  The cavity beneath the junction of the arm and the body, better known as the armpit.
Axis: The axis is the second cervical vertebra (symbol: C2). It is called the "axis" because the uppermost cervical vertebra (cal:  
Axon:  A long fiber of a nerve cell (a neuron) that acts somewhat like a fiber-optic cable carrying outgoing (efferent) messages. The neuron sends electrical impulses from its cell body through the axon to target cells. Each nerve cell has one axon. An axon can be over 20 cm (a foot) in length. A motor neuron (a single cell) stretching from the motor context to the end of the spinal cord would be about three feet long.
Ayurveda:  India's traditional, natural system of medicine that has been practiced for more than 5,000 years. Ayurveda provides an integrated approach to preventing and treating illness through lifestyle interventions and natural therapies. Ayurvedic theory states that all disease begins with an imbalance or stress in the individual's consciousness. Lifestyle interventions are a major ayurvedic preventive and therapeutic approach.
Azoospermia:  No sperm at all. The ejaculate is completely devoid of sperm.
Azotemia:  A higher than normal blood level of urea or other nitrogen containing compounds in the blood. The hallmark test is the serum BUN (blood urea nitrogen) level. Usually caused by the inability of the kidney to excrete these compounds.
AZT:  Zidovudine (formerly called azidothymidine [abbreviated AZT]), a drug used against human immunodeficiency virus (HIV), the virus that causes AIDS. The brand name is Retrovir. The US Food and Drug Administration (FDA) approved AZT for the treatment of HIV infection. Current practice favors the use of AZT in combination with other drugs. Oddly enough the side-effects of AZT are identical to the effects of AIDS and there is a minority opinion among doctors that AZT causes AIDS.

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