MEDICAL DICTIONARY
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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B cells: A type of white blood cell. Many B cells mature into plasma cells, which can produce antibody proteins necessary to fight off infections, such as viruses.
Baby, fetal alcohol syndrome: Alcohol is capable of causing birth defects. FAS (fetal alcohol syndrome) always involves brain damage. and impaired growth. FAS also always involves head and face abnormalities. No amount of alcohol has been proven safe during pregnancy. Women who are or may become pregnant are advised to avoid alcohol.

Back pain, low: Symptoms in the low back can relate to the bony lumbar spine, discs between the vertebrae, ligaments around the spine and discs, spinal cord and nerves, muscles of the low back, internal organs of the pelvis and abdomen, and the skin covering the lumbar area. The low back, or lumbar area, functions in structural support, movement, and protection of certain body tissue.

Bacteria: are single-celled microorganisms which can live as either independent organisms or as parasites. It is a bacteria that is responsible for the common throat infection "Strep throat."

Bacteriophage: A virus that naturally lives within a bacterial cell. Much used in molecular genetics and cell biology. Known commonly as phage.

"Bad" cholesterol: Low-density lipoprotein (LDL) cholesterol.

Baker’s cyst: A swelling in the space behind the knee (the popliteal space) composed of a membrane-lined sac filled with synovial fluid that has escaped from the joint. Named after the British surgeon William Morrant Baker (1839-1896). Also called a synovial cyst of the popliteal space.

Baldness: Alopecia. There are many types of baldness, each with a different cause. Baldness can be localized to the front and top of the head, such as in male pattern baldness; patchy, such as in alopecia areata; or involve the entire head, such as in alopecia capitis totalis.

Baldness, patchy: Medically referred to as alopecia areata (alopecia means baldness and areata means occurring in patches). The problem typically begins with patchy hair loss on the scalp and sometimes progresses to complete baldness and even loss of body hair. Although alopecia areata affects 2.5 million people in the United States alone, little is known about its underlying causes. Stress, a disordered immune system, and several different unknown genes may possibly play a part.

Balloon angioplasty: Coronary angioplasty is accomplished using a balloon-tipped catheter inserted through an artery in the groin or arm to enlarge a narrowing in a coronary artery. Coronary artery disease occurs when cholesterol plaque builds up (atherosclerosis) in the walls of the arteries to the heart. Angioplasty is successful in opening coronary arteries in 90% of patients. 40% of patients with successful coronary angioplasty will develop recurrent narrowing at the site of balloon inflation.

Banding of chromosomes: Treatment of chromosomes to reveal characteristic patterns of horizontal bands. Thanks to these banding patterns that resemble bar codes, each human chromosome is distinctive and can be identified without ambiguity.

Barium enema: A series of x-rays of the lower intestine. The x-rays are taken after the patient is given an enema with a white, chalky solution that contains barium. The barium outlines the intestines on the x-rays.

Barium solution: A liquid containing barium sulfate, which shows up on x-rays. It outlines organs of the body so they can be seen on x-ray film.

Barium swallow: An upper gastrointestinal series (barium swallow) is an X-ray test used to define the anatomy of the upper digestive tract. Women who are or may be pregnant should notify the doctor requesting the procedure and the radiology staff. The test involves filling the esophagus, stomach, and small intestines with a white liquid material (barium).

Barlow’s syndrome: Barlow’s syndrome is mitral valve prolapse (also known as "click murmur syndrome"), the most common heart valve abnormality, affecting 5-10% of the world population. Most patients have no symptoms and require no treatment. However, the condition can be associated with fatigue and/or palpitations. The mitral valve prolapse can often be detected by a doctor during examination of the heart and can be confirmed with an echocardiogram. Patients are usually given antibiotics prior to any procedure which might introduce bacteria into the bloodstream, including dental work and minor surgery.

Barr body: A microscopic feature of female cells due to the presence of two X chromosomes in the female. One of these X chromosomes is inactive and is crumpled up to form the Barr body.

Barrett's esophagus: A change in the cells of the tissue that lines the bottom of the esophagus. The esophagus may become irritated when the contents of the stomach back up (reflux). Reflux that happens often over a period of time can lead to Barrett's esophagus. Barrett’s esophagus is a risk factor in esophageal cancer.

Basal cells: Small, round cells found in the lower part, or base, of the epidermis, the outer layer of the skin.

Basal cell carcinoma: A type of skin cancer in which the cancer cells resemble the basal cells of the epidermis.

Basal metabolic rate: A measure of the rate of metabolism. For example, someone with an overly active thyroid will have an elevated basal metabolic rate.

Base in DNA: A unit of the DNA. There are 4 bases: adenine (A), guanine (G), thymine (T), and cytosine (C). The sequence of bases (for example, CAG) is the genetic code.

Base pair: Two DNA bases complementary to one another (A and T or G and C) that join the complementary strands of DNA to form the double helix characteristic of DNA.

Base sequence: The order of nucleotide bases (A,T, G, C) in a DNA molecule.

Base sequence analysis: A method for determining the order of nucleotide bases in DNA.

Battle fatigue: The World War II name for what is known today as post-traumatic stress, this is a psychological disorder that develops in some individuals who have had major traumatic experiences (and, for example, have been in a serious accident or through a war). The person is typically numb at first but later has symptoms including depression, excessive irritability, guilt (for having survived while others died), recurrent nightmares, flashbacks to the traumatic scene, and overreactions to sudden noises. Post-traumatic stress became known as such in the 70s due to the adjustment problems of some Vietnam veterans.

Bee stings: Stings from bees and other large stinging insects such as yellow jackets, hornets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)

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. Also known as the African tapeworm.

Behcet’s syndrome: Behcet’s syndrome is classically characterized as a triad of symptoms that include recurring crops of mouth ulcers (called apthous ulcers), genital ulcers, and inflammation of a specialized area around the pupil of the eye, the uvea. (The inflammation is called uveitis.) The cause of Behcet’s syndrome is not known. The disease is more frequent and severe in patients from the Eastern Mediterranean and Asia than those of European descent.

Belching: A normal process to relieve distention from the air that accumulates in the stomach. The upper abdominal discomfort associated with excessive swallowed air may extend into the lower chest, producing symptoms suggesting heart or lung disease.

Belly button: The navel or umbilicus. The one-time site of attachment of the umbilical cord. The term "belly button" was coined around 1877.

Benign: Not cancer; does not invade surrounding tissue or spread to other parts of the body.

Benign prostatic hypertrophy (BPH): Nonmalignant (noncancerous) enlargement of the prostate gland, a common occurrence in older adult men.

Bernard syndrome: A complex of abnormal findings, namely sinking in of one eyeball, ipsilateral ptosis (drooping of the upper eyelid on the same side) and miosis (constriction of the pupil of that eye) together with anhidosis (lack of sweating) and flushing of the affected side of the face. Due to paralysis of certain nerves (specifically, the cervical sympathetic nerves). Also called Horner-Bernard syndrome, Bernard-Horner syndrome and Horner’s ptosis, but best known today as Horner syndrome.

Beta blockers: A class of drugs that block the action of adrenaline (a beta adrenergic substance) and can relieve stress to the heart muscle. Beta blockers are often used to slow the heart rate or lower the blood pressure.

Beta carotene: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mushed carrots.

Beta error: The statistical error (said to be "of the second kind" or type II) made in testing when it is concluded that something is negative when it really is positive. Beta error is often referred to as a false negative.

Bias: In a clinical trial, bias refers to effects that a conclusion that may be incorrect as, for example, when a researcher or patient knows what treatment is being given. To avoid bias, a blinded study may be done.

Bicornuate: Having two horns or horn-shaped branches. The uterus (normally unicornuate) can sometimes be bicornuate (with two branches, eg, one at about 10:30 and the other at about 1:30).

Bifid: Cleft (split) in two. See, for example, bifid uvula.

Bifid uvula: The uvula, the little V-shaped fleshy mass hanging from the back of the soft palate, is cleft or split. Cleft uvula is a common minor anomaly occurring in about 1% of whites and 10% of Native Americans. Persons with a cleft uvula should not have their adenoids removed because, without the adenoids, they cannot achieve proper closure between the soft palate and pharynx while speaking and develop hypernasal speech.

Bile: A yellow-green fluid made by the liver. Bile is stored in the gallbladder. It passes through the common bile duct into the duodenum, where it helps digest fat.

Bilharzia: Disease caused by worms that parasitize people. Also called schistosomiasis.. Three main species of these trematode worms (flukes)--Schistosoma haematobium, S. japonicum, and S. mansoni—cause disease in humans. Larval forms of the parasite live in freshwater snails. The cercaria (form of the parasite) is liberated from the snail burrow into skin, transforms to the schistosomulum stage, and migrates to the urinary tract (S. haematobium), liver or intestine (S. japonicum, S.mansoni) where the adult worms develop. Eggs are shed into the urinary tract or the intestine and hatch to form miracidia (yet another form of the parasite) which then infect snails, completing the life cycle of the parasite.. Adult schistosome worms can seriously damage tissue. The name bilharzia comes from that of the shortlived German physician Theodor Bilharz (1825-1862).

Bilharziasis: a parasite infection by a trematode worm acquired from infested water. Also known as schistosomiasis. Species which live in man can produce liver, bladder, and gastrointestinal problems. Species of the schistosomiasis parasite which cannot live in man cause swimmer’s itch.

Bilirubin: A yellow-orange compound produced by the breakdown of hemoglobin from red blood cells.

Biologic evolution: Biologic evolution was contrasted with cultural evolution in 1968 by A.G. Motulsky who pointed out that biologic evolution is mediated by genes, shows a slow rate of change, employs random variation (mutations) and selection as agents of change, new variants are often harmful, these new variants are transmitted from parents to offspring, the mode of transmission is simple, complexity is achieved by the rare formation of new genes by chromosome duplication, biologic evolution occurs with all forms of life, and the biology of humans requires cultural evolution. See Cultural evolution.

Biological response modifiers: Substances that stimulate the body's response to infection and disease. The body naturally produces small amounts of these substances. Scientists can produce some of them in the laboratory in large amounts and use them in cancer treatment. Also called BRMs.

Biological therapy: Treatment to stimulate or restore the ability of the immune (defense) system to fight infection and disease. Also called immunotherapy.

Biopsy: The removal of a sample of tissue for examination under a microscope to check for cancer cells. A specialist trained to examine such tissues is called a pathologist.

Biotechnology: The fusion of biology and technology. Biotechnology is the application of biological techniques to product research and development. In particular, biotechnology involves the use by industry of recombinant DNA, cell fusion, and new bioprocessing techniques. Biotechnology is expected to become increasingly important in the 21st century.

Bipolar disease: A type of depressive disease, formerly called manic-depressive illness. Not nearly as prevalent as other forms of depressive disorders, bipolar disorder involves cycles of depression and elation or mania. Sometimes the mood switches are dramatic and rapid, but most often they are gradual. Mania often affects thinking, judgment, and social behavior in ways that cause serious problems and embarrassment. For example, unwise business or financial decisions may be made when an individual is in a manic phase. Bipolar disorder is often a chronic recurring condition.

Birth rate: The birth rate is usually given as the number of live births divided by the average population (or the population at midyear). This is termed the crude birth rate. In 1995, for example, the crude birth rate per 1,000 population was 14 in the United States, 16.9 in Australia, etc.

Black death: The black plague, i.e., the plague. In 14th-century Europe, the victims of the "black plague" had bleeding below the skin (subcutaneous hemorrhage) which made darkened ("blackened") their bodies. Black plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose. Black plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea.

Black plague: In 14th-century Europe, the victims of the "black plague" had bleeding below the skin (subcutaneous hemorrhage) which made darkened ("blackened") their bodies. Black plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose. Black plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea.

Bladder: The organ that stores urine.

Bladder cancer: The most common warning sign of bladder cancer is blood in the urine. The diagnosis of bladder cancer is supported by findings in the medical history and examination, blood, urine, and x-ray tests, and confirmed with a biopsy (usually during a cystoscope exam). Treatment of bladder cancer depends on the growth, size, and location of the tumor.

Bladder cancer risks: Smoking is a major risk factor. Cigarette smokers develop bladder cancer 2-3 times more often than do nonsmokers. Quitting smoking reduces the risk of bladder cancer, lung cancer, several other types of cancer, and a number of other diseases as well. Workers in some occupations are at higher risk of developing bladder cancer because of exposure to carcinogens (cancer-causing substances) in the workplace. These workers include people in the rubber, chemical, and leather industries, as well as hairstylists, machinists, metal workers, printers, painters, textile workers, and truck drivers.

Bladder infection: Some people are at more risk for bladder and other urinary tract infections (UTIs) than others. One woman in five develops a UTI during her lifetime. Not everyone with a UTI has symptoms. Common symptoms include a frequent urge to urinate and a painful, burning when urinating. Underlying conditions that impair the normal urinary flow can lead to more complicated UTIs.

Bladder inflammation: Also referred to as cystitis. Cystitis most commonly occurs because of bacterial infection. Another form of bladder inflammation, interstitial cystitis (IC) involves inflammation or irritation of the bladder wall. This can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes IC, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments.

Bladder pain: Among the symptoms of bladder infection are feelings of pain, pressure and tenderness around the bladder, pelvis, and perineum (the area between the anus and vagina or anus and scrotum), which may increase as the bladder fills and decrease as it empties; decreased bladder capacity; an urgent need to urinate; painful sexual intercourse; and, in men, discomfort or pain in the penis and scrotum.

Blast phase: Refers to advanced chronic myelogenous leukemia. In this phase, the number of immature, abnormal white blood cells in the bone marrow and blood is extremely high. Also called blast crisis.

Blasts: Immature blood cells.

Bleb: A bladderlike structure more than 5 mm in diameter with thin walls that may be full of fluid. Also called a bulla.

Blepharospasm: The involuntary, forcible closure of the eyelids. The first symptoms may be uncontrollable blinking. Only one eye may be affected initially, but eventually both eyes are usually involved. The spasms may leave the eyelids completely closed causing functional blindness even though the eyes and vision are normal. Blepharospasm is a form of focal dystonia.

Blinded study: Clinical trials of drugs are often done blinded so that the patient does not know (is blinded as to) whether they are receiving the product being tested or the control/placebo to ensure that the results of a study are not affected by a possible placebo effect (by the power of suggestion).

Blood: The blood is the fluid in the body that contains red and white cells as well as platelets, proteins, plasma and other elements. It is transported throughout the body by the circulatory system.

Blood-brain barrier: A protective network of blood vessels and cells that filters blood flowing to the brain.

Blood group: An inherited feature on the surface of the red blood cell. A series of related blood groups make up a blood group system such as the ABO system or the Rh system.

Blood pressure: The blood pressure is the pressure of the blood within the arteries. It is produced primarily by the contraction of the heart muscle. It's measurement is recorded by two numbers. The first (systolic pressure) is measured after the heart contracts and is highest. The second (diastolic pressure) is measured before the heart contracts and lowest. A blood pressure cuff is used to measure the pressure. Elevation of blood pressure is called "hypertension." (see hypertension).

Blood pressure, high: High blood pressure (hypertension) is a repeatedly elevated blood pressure exceeding 140 over 90 mmHg. High blood pressure is also called "the silent killer." Chronically high blood pressure can cause blood vessel changes in the back of the eye (retina), thickening of the heart muscle, kidney failure, and brain damage. No specific cause for high blood pressure is found in 95% of patients. High blood pressure is treated with salt restriction, regular aerobic exercise, and medications.

Blood sugar, low: The sugar here is glucose. Low blood glucose constitutes hypoglycemia . Hypoglycemia is only significant when it is associated with symptoms. It has many causes including drugs, liver disease, surgical absence of the stomach, pre-diabetes, and rare tumors that release excess insulin.

Blood sugar, high: Elevated levels of blood glucose (hyperglycemia) can be found in a number of conditions. The hyperglycemia leads to spillage of glucose into the urine, hence the term sweet urine. (Diabetes mellitus means "sweet urine.")

Blood-thinner: An anticoagulant.

Blood transfusion: The transfer of blood or blood products from one person (donor) into another person’s bloodstream (recipient). In most situations this is done as a life saving maneuver to replace blood cells or blood products lost through severe bleeding. Transfusion of your own blood (autologous) is the safest method but requires planning ahead and not all patients are eligible. Directed donor blood allows the patient to receive blood from known donors. Volunteer donor blood is usually readily available and when properly tested has a low incidence of adverse events. Blood conserving techniques are an important aspect of limiting transfusion requirements.

Blood urea nitrogen (BUN): A measure primarily of the urea level in blood. Urea is cleared by the kidney. Diseases that compromise the function of the kidney frequently lead to increased blood levels.

Blood, urinary: Medically called hematuria, blood in the urine can be microscopic or gross. Evaluating hematuria requires consideration of the entire urinary tract. Tests used for the diagnosis of hematuria include the intravenous pyelogram (IVP), cystoscopy, and urine cytology. Management of hematuria depends upon the underlying cause.

Bloody show: Literally, the appearance of blood. The bloody show consists of blood-tinged mucus created by extrusion and passage of the mucous plug that filled the cervical canal (the canal between the vagina and uterus) during pregnancy. The bloody show is therefore a classic sign of impending labor. The same term, bloody show, can be applied to the beginning of menstruation.

Blot, Northern: A technique in molecular biology, used mainly to separate and identify pieces of RNA. Called a Northern blot only because it is similar to a Southern blot (which is named after its inventor, the British biologist M.E. Southern).

Blot, Southern: A common test for checking for a match between DNA molecules. DNA fragments are separated by agarose gel electrophoresis, transferred (blotted) onto membrane filters, and hybridized with complementary radiolabeled probes. The aim is to detect specific base sequenceswith the probes. Lest all of this sound esoteric, note that in the television series "The X Files" a Southern blot was done (in this case, to learn if some alien virus genome had been integrated into a person’s genome). The Southern blot is named after its inventor, the British biologist M.E. Southern. There is also a Northern blot and a Western blot.

Blot, Western: A technique in molecular biology, used to separate and identify proteins. Called a Western blot merely because it has some similarity to a Southern blot (which is named after its inventor, the British biologist M.E. Southern).

Boils: A skin abscess, a collection of pus that forms inside the body. Antibiotics are often not very helpful in treating abscesses. The main treatments include hot packs and draining ("lancing") the abscess, but only when it is soft and ready to drain. If you have a fever or long-term illness, such as cancer or diabetes, or are taking medications that suppress the immune system, you should contact your healthcare practitioner if you develop an abscess.

Bone: Bone is the substance that forms the skeleton of the body. It is composed chiefly of calcium phosphate and calcium carbonate. It also serves as a storage area for calcium, playing a large role in calcium balance in the blood.

Bone cancer: Cancers that begin in bone are rare but it is not unusual for cancers to spread to bone from other parts of the body. This is not called bone cancer, but is named for the organ or tissue in which the cancer begins. Pain is the most frequent symptom of cancer of the bone. Diagnosis of cancer of the bone is supported by findings of the medical history and examination, blood and x-ray tests and confirmed with a biopsy. Treatment of cancer of the bone depends on the type, location, size, and extent of the tumor as well as the age and health of the patient.

Bone density: Bone density is the amount of bone tissue in a certain volume of bone. It can be measured using a special x-ray called a quantitative computed tomogram.

Bone marrow: The bone marrow is the soft substance that fills bone cavities. It is composed of mature and immature blood cells and fat. The blood cells include white blood cells, red blood cells and platelets. Diseases or drugs that affect the bone marrow can affect the "total counts" of these cells.

Bone marrow aspiration: The removal of a small sample of bone marrow (usually from the hip) through a needle for examination under a microscope to see whether cancer cells are present.

Bone marrow biopsy: The removal of a small piece of bone and bone marrow (usually from the hip) through a large needle. The sample is examined under a microscope to see whether cancer cells are present.

Bone marrow transplantation: A procedure in which doctors replace diseased bone marrow with healthy bone marrow. The diseased bone marrow is destroyed by high doses of chemotherapy and/or radiation therapy. The replacement marrow may come from another person, or it may be the patient's own marrow (which was removed and stored before treatment). When donated marrow is used, the procedure is usually called allogeneic bone marrow transplantation. Autologous bone marrow transplantation uses the patient's own marrow.

Bone scan: A technique to create images on bones on a computer screen or on film. A small amount of radioactive material is injected and travels through the bloodstream. It collects in the bones, especially in abnormal areas of the bones, and is detected by a scanner.

Boutonneuse: Fièvre boutonneuse or 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. The French word "boutonneuse" means pimply. Also called Conor and Bruch’s disease.

Bowel: Another name for the intestine. There is both a small and a large bowel.

Bowel disorders and fiber: High fiber diets help delay the progression of diverticulosis and, at least, reduce the bouts of diverticulitis. In many cases, it helps reduce the symptoms of the Irritable Bowel Syndrome ( IBS ). It is generally accepted that a diet high in fiber is protective, or at least reduces the incidence, of colon polyps and colon cancer.

bp: In genetics, base pair. In general medicine, blood pressure (but usually in capital letters as BP).

BP: Commonly used abbreviation for blood pressure. For example, in a medical chart, you might see scrawled "BP90/60 T98.6 Ht60/reg R15", which is short hand signifying that the blood pressure is 90/60 mm Hg, the temperature (T) is 98.6 degrees Fahrenheit, the heart rate (Ht) is 60 beats/min and regular, and the respirations ® 15/min. (This would be entirely normal for an adult or older child).

BPH: Benign prostatic hypertrophy. Nonmalignant enlargement of the prostate gland.

Brachial plexus: A bundle of nerves beginning in the posterior base of the neck and extending through the axilla. I is formed by the union of portions of the fifth through eighth cervical spinal nerves and first thoracic spinal nerve. Damage to the brachial plexus can affect nerves supplying the arm and chest.

Bradycardia: A slow heart rate, usually defined as less than 60 beats per minute.

Brain: The brain is that portion of the central nervous system that is located within the skull. It functions as a primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

Brain stem: The stemlike part of the brain that is connected to the spinal cord.

Brain stem glioma: A type of brain tumor.

Brain tumors: Can be malignant or benign and can occur at any age. Primary brain tumors initially form in the brain tissue. Secondary brain tumors are cancers that have spread to the brain tissue (metastasized) from tissue elsewhere in the body.

Branchial cleft cyst: Also called a branchial cyst, this is a cavity that is a remnant from embryologic development present at birth in one side of the neck just in front of the large angulated muscle on either side (the sternocleidomastoid muscle). The cyst may not be recognized until adolescence as it enlarges its oval shape. Sometimes it develops a sinus or drainage pathway to the surface of the skin from which mucus can be expressed. Total surgical excision is the treatment of choice. Recurrence is not expected.

Branchial cyst: Also called a branchial cleft cyst, this is a cavity that is a remnant from embryologic development present at birth in one side of the neck just in front of the large angulated muscle on either side (the sternocleidomastoid muscle). The cyst may not be recognized until adolescence as it enlarges its oval shape. It may develop a sinus or drainage pathway to the surface of the skin from which mucus can be expressed. Total surgical excision is the treatment of choice. Recurrence is not expected.

BRCA1: A gene that normally acts to restrain the growth of cells. (The symbol BRCA comes from BReast CAncer).

BRCA1 breast cancer susceptibility gene: This mutated (changed) version of the BRCA1 gene makes a person susceptible to developing breast cancer.

Breast: The anterior aspect of the chest or the mammary gland. The latter is composed of primarily fat in which there is a complex branching duct network from the nipple inward. In the female, lobules develop at the end of the ducts to produce milk.

Breast augmentation: Enlargement of the breasts. Augmentation of the breast typically consists of insertion of a silicone bag (prosthesis) under the breast (submammary) or under the breast and chest muscle (subpectoral) and then filling the bag with saline (salt water). This prosthesis expands the breast area to give a fuller breast (increased cup size), give a better contour, and give better cleavage.

Breast cancer: Breast cancer is diagnosed with self- and physician-examination of the breasts, mammography, ultrasound testing, and biopsy. There are many types of breast cancer that differ in their capability of spreading to other body tissues (metastasis). Treatment of breast cancer depends on the type and location of the breast cancer, as well as the age and health of the patient. The American Cancer Society recommends that a woman should have a baseline mammogram between the ages of 35 and 40 years. Between 40 and 50 years of age mammograms are recommended every other year. After age 50 years, yearly mammograms are recommended.

Breast cancer, familial: A number of factors have been identified that increase the risk of breast cancer. One of the strongest of these risk factors is the history of breast cancer in a relative. About15-20% of women with breast cancer have such a family history of the disease, clearly reflecting the participation of inherited (genetic) components in the development of some breast cancers. Dominant breast cancer suceptibility genes, including BRCA1 and BRCA2, appear responsible for about 5% of all breast cancer. See related entries to: Breast cancer susceptibility genes; BRCA1; BRCA2.

Breast cancer susceptibility genes: Inherited factors that predispose to breast cancer. Put otherwise, these genes make one more susceptible to the disease and so increase the risk of developing breast cancer. Two of these genes, BRCA1 and BRCA2, have been identified (and prominently publicized). Several other genes (those for the Li-Fraumeni syndrome, Cowden disease, Muir-Torre syndrome, and ataxia-telangiectasia) are also known to predispose to breast cancer. However, since all of these known breast cancer susceptibility genes together do not account for more than a minor fraction (1/5th at most) of breast cancer that clusters in families, it is clear that more breast cancer genes remain to be discovered.

Breast feeding: The ability of the breast to produce milk diminishes soon after childbirth without the stimulation of breastfeeding. Immunity factors in breast milk can help the baby to fight off infections. Breast milk contains vitamins, minerals, and enzymes which aid the baby’s digestion. Breast and formula feeding can be used together.

Breech: The buttocks.

Breech delivery: Literally, delivery of the baby by the buttocks first (as opposed to the head. The "Good Word" according to The Florida Times-Union of Feb. 10, 1998 is "Breech delivery—Birth, feet first." This is, of course, wrong. It should be: "Breech delivery—Birth, buttocks first."

Bridge teeth are false teeth that replace on or more missing teeth supported by a metal framework.

Brill-Zinsser disease: Recrudescence of epidemic typhus years after the initial attack. The agent that causes epidemic typhus (Rickettsia prowazekii) remains viable for many years and then when host defenses are down, it is reactivated causing recurrent typhus. The disease is named for the physician Nathan Brill and the great bacteriologist Hans Zinsser.

Bronchi: The large air tubes which begin at the end of the trachea and branch into the lungs. Characterized by having cartilage as part of the supporting wall structure.

Bronchioles: The tiny branches of air tubes within the lungs which are the continuation of bronchi and connect to the alveoli (air sacs).

Bronchitis: Inflammation (swelling and reddening) of the bronchi.

Bronchopulmonary segments: A subdivision of one lobe of a lung based on the connection to the segmental bronchus. For example, the right upper lobe has apical, anterior, and posterior segments.

Bronchoscope: A thin, flexible instrument used to view the air passages of the lung.

Bronchoscopy: A test that permits the doctor to see the breathing passages through a lighted tube.

Brown’s syndrome: An ophthalmology (eye) problem. Brown’s syndrome presents as an abnormality at birth (congenitally) and is characterized by an inability to elevate the eyeball when also trying to move the eyeball to the outside. Brown’s syndrome can also occur because of other conditions which affect the normal function of the eye muscles.

Bruise: A bruise or "contusion" is an traumatic injury of the soft tissues which results in breakage of the local capillaries and leakage of red blood cells. In the skin it can be seen as a reddish-purple discoloration which does not blanch when pressed upon. When it fades it becomes green and brown as the body metabolizes the blood cells in the skin. It is best treated with local application of a cold pack immediately after injury.

Bubo: An enlarged lymph node ("swollen gland") that is tender and painful, particularly in the groin and armpit (the axilla). A feature of a number of infectious diseases including gonorrhea, syphilis, tuberculosis, and the plague. Hence, the bubonic plague. The odd word "bubo" comes from the Greek "boubon" meaning groin or swollen groin.

Buboes: The plural of "bubo".

Bubonic plague: The most common form of the plague named for the characteristic buboes which are enlarged lymph nodes ("swollen glands") in the groin that are tender and painful. Lymph nodes may be similarly affected in the armpits (axillae), neck and elsewhere. Other features of the bubonic plague include headache, fever, chills, and weakness. Bubonic plague is caused by a bacterium (Yersinia pestis) which is transmitted to humans from infected rats by the oriental rat flea. Bubonic plague can lead to "black death" characterized by gangrene of the fingers, toes, and nose.

Buccal mucosa: The inner lining of the cheeks and lips.

Bulimia: An insatiable appetite, often interrupted by periods of anorexia. Bulimia is a psychological disorder that can be accompanied by self-induced vomiting.

Bulla: A blister more than 5 mm in diameter with thin walls that is full of fluid. Also called a bleb.

Bullous: Characterized by blistering, such as in second-degree burn.

Bullous pemphiguoid: A disease characterized by tense blistering eruptions of the skin. caused by antibodies abnormally accumulating in a layer of the skin called the "basement membrane." Can be chronic and mild without affecting the general health. It is diagnosed by skin biopsy showing the abnormal antibodies deposited in the skin layer. Treatment is with topical cortisone creams, but sometimes requires high doses of cortisone ("steroids") taken internally.

Bumps: The raised area of a bump or bruise results from blood leaking from these injured blood vessels into the tissues as well as from the body’s response to the injury. A purplish, flat bruise that occurs when blood leaks out into the top layers of skin is referred to as an ecchymosis.

BUN: Blood urea nitrogen. A measure primarily of the urea level in blood. Urea is cleared by the kidney and diseases which compromises the function of the kidney will frequently lead to increased blood levels.

Bunion: A bunion is a localized painful swelling at the base of the big toe. It is frequently associated with inflammation. It can be related to inflammation of the nearby bursa (bursitis) or degenerative joint disease (osteoarthritis).

Burkitt's lymphoma: A type of non-Hodgkin's lymphoma that most often occurs in young people between the ages of 12 and 30. The disease usually causes a rapidly growing tumor in the abdomen.

Burns: The treatment of burns depends on the depth, area and location of the burn. Burn depth is generally categorized as first, second or third degree. A first degree burn is superficial and has similar characteristics to a typical sun burn. The skin is red in color and sensation is intact. In fact, it is usually somewhat painful. Second degree burns look similar to the first degree burns; however, the damage is now severe enough to c ause blistering of the skin and the pain is usually somewhat more intense. In third degree burns the damage has progressed to the point of skin death. The skin is white and without sensation.

Burns, first degree: A first degree burn is superficial and has similar characteristics to a typical sun burn. The skin is red in color and sensation is intact. In fact, it is usually somewhat painful.

Burns, second degree: Second degree burns look similar to the first degree burns in that it is red and sensation is intact; however, the damage is severe enough to cause blistering of the skin and the pain is usually somewhat more intense.

Burns, third degree: In third degree burns the damage has progressed to the point of skin death. The skin is white and without sensation.

Bursa: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known to as "bursitis." Most commonly this is not an infectious condition (aseptic bursitis). When the bursa is infected with bacteria, the condition is called septic bursitis. Bypass: An operation in which the surgeon creates a new pathway for the movement of substances in the body.

Bursitis: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known to as "bursitis."

Bursitis, aseptic: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." Most commonly this is not an infectious condition (aseptic bursitis).

Bursitiis, calcific: A bursa is a thin fluid-filled sac that reduces friction forces between tissues of the body. Chronic (repeated of long-standing) inflammation of the bursa (bursitis) can lead to calcification of the bursa. This is referred to as "calcific bursitis." The calcium deposition (calcification) can occur as long as the inflammation is present.

Bursitis, elbow: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. The bursa at the tip of the elbow is called the olecranon bursa. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.

Bursitis, hip: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the hip. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.

Bursitis, knee: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are three major bursae of the knee. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.

Bursitis, septic: A bursa is a closed fluid-filled sac that functions as a gliding surface to reduce friction between tissues of the body. When the bursa becomes inflamed, the condition is known as "bursitis." When the bursa is infected with bacteria, the condition is called septic bursitis.

Bursitis, shoulder: A bursa is a fluid-filled sac that functions as a gliding surface to reduce friction between moving tissues of the body. There are two major bursae of the shoulder. Bursitis is usually not infectious, but the bursa can become infected. Treatment of non-infectious bursitis includes rest, ice, and medications for inflammation and pain. Infectious bursitis is treated with antibiotics, aspiration, and surgery.

Bypass (Coronary Artery Bypass Graft): Coronary artery disease develops because of hardening of the arteries (atherosclerosis) that supply blood to the heart muscle. Diagnostic tests include EKG, stress test, echocardiography, and coronary angiography. Coronary artery bypass graft (CABG) surgery is advised for selected groups of patients with significant narrowings and blockages of the heart arteries (coronary artery disease) to create new routes around narrowed and blocked arteries, permitting increased blood flow to deliver oxygen and nutrients to the heart muscles. The bypass graft for a CABG can be a vein from the leg or an inner chest wall artery. CABG surgery is performed about 350,000 times annually in the United States, making it one of the most commonly performed major operations.

Bypass, cardiopulmonary: Bypass of the heart and lungs as, for example, in open heart surgery. Blood returning to the heart is diverted through a heart-lung machine (a pump-oxygenator) before returning it to the arterial circulation. The machine does the work both of the heart (pump blood) and the lungs (supply red blood cells with oxygen).