Medical Glossary Index:

B

Bacillus- any bacteria that is rod-shaped; responsible for diphtheria, dysentery, tetanus, and tuberculosis, as well as other diseases

Bacteremia- a condition in which bacteria are present in the bloodstream; may occur after minor surgery or infection and may be dangerous for people with a weakened immune system or abnormal heart valves

Bacteriostatic- term used to describe a substance that stops the growth of bacteria (such as an antibiotic)

Bacterium- a tiny, single-celled microorganism, commonly known as a germ; some bacteria, called pathogens, cause disease

Bacteriuria- bacteria in the urine; large amounts can indicate bladder, urethra, or kidney infection

Ball-and-socket joint- a joint consisting of a ball-shaped bone that fits into a cup-shaped bone, making the joint free to rotate; examples include the hip and shoulder

Balloon angioplasty- a technique that uses a balloon catheter to open arteries clogged with fatty deposits

Balloon catheter- a hollow tube with a small, inflatable balloon at the tip; used to open a narrowed artery or organ that has become blocked

Barbiturates- a group of sedatives that reduce activity in the brain; are habit-forming and are possibly fatal when taken with alcohol

Barium enema- a technique in which barium is placed into the large intestine and rectum and then X-rays are taken to check for possible disorders of these organs

Barrier method of contraception- a birth-control technique using a condom, diaphragm, or another similar device to block the path of sperm to an egg

Bartholin's glands- two pea-sized glands that, when sexually aroused, release a fluid that lubricates the vagina

Basal cell carcinoma- a type of skin cancer that is caused by exposure to large amounts of sunlight; commonly found on the neck, face, and arms

Basal metabolic rate- the lowest rate at which a person can possibly use energy and remain alive; at this rate, only absolutely necessary functions such as breathing are maintained

B cell- a white blood cell that makes antibodies to fight infections caused by foreign proteins

BCG vaccine- a vaccine used to protect against tuberculosis

Becker’s muscular dystrophy- a hereditary disease in which the muscles weaken and waste away; similar to Duchenne muscular dystrophy but starts later in life and advances more slowly

Bell's palsy- another name for facial palsy, the usually one-sided, temporary numbing of the facial muscles, caused by an inflamed nerve

Bends- see Decompression sickness

Benign tumor- a tumor that is not cancerous, which means it does not spread through the body, but may grow and become dangerous

Beta blocker- a type of drug used to treat high blood pressure and heart disorders by reducing the strength and rate of the pumping by the heart

Beta carotene- a pigment found in orange vegetables and fruits, which the body converts to vitamin A; possibly protects against cancer

Bifocal- a lens that corrects both near and distant vision by having two parts with different focusing strengths

Bilateral- a term describing a condition that affects both sides of the body or two paired organs, such as bilateral deafness (deafness in both ears)

Bile- a yellow-green liquid produced in the liver whose function is to remove waste from the liver and break down fats as food is digested

Bile duct- a tube that carries bile from the liver to the gallbladder and then to the small intestine

Biliary atresia- a birth defect in which the bile ducts are not completely developed; often a liver transplant is necessary

Biliary colic- a severe pain in the upper right section of the abdomen, usually caused by a gallstone passing out of the bladder or through the bile ducts

Biliary tract- the system of organs and ducts through which bile is made and transported from the liver to the small intestine

Bilirubin- the orange-yellow pigment in bile, causing jaundice if it builds up in the blood and skin; the levels of bilirubin in the blood are used to diagnose liver disease

Binging and purging- behavior characteristic of the disorder bulimia in which a person overeats then rids themselves of the food before it can be absorbed by the body, either by forced vomiting or through the use of laxatives

Biochemistry- the science that studies the chemistry of living organisms, including humans

Bioequivalent- a drug that has the same effect on the body as another drug

Biofeedback- a technique used to gain control over a function that is normally automatic (such as blood pressure or pulse rate); the function is monitored and relaxation techniques are used to change it to a desired level

Bipolar disorder- an illness in which the patient goes back and forth between opposite extremes; the most notable bipolar disorder is manic-depressive disorder, which is characterized by extreme highs and lows in mood

Birth canal- the passage that includes the uterus and vagina through which the baby passes at birth

Birth control- the regulation of the number of children born, referring either to the prevention of pregnancy (by birth control pill, sterilization, etc) or the prevention of birth (by abortion, etc)

Birth defect- an abnormality that is present when a baby is born

Birthmark- any area of discolored skin that is present when a baby is born

Bisexuality- sexual interest in members of both sexes

Bladder- an organ located in the pelvis whose function is to collect and store urine until it is expelled

Blepharitis- inflammation of the eyelids

Blind spot- a spot in the field of vision that is not sensitive to light; it is a product of the entrance of the optic nerve into the eyeball, where no light receptors are present on the retina

Blood-brain barrier- a layer of tightly bound cells that prevents certain substances carried in the bloodstream from entering the brain

Blood clot- a semisolid mass of blood that forms to help seal and prevent bleeding from a damaged vessel

Blood poisoning- see Septicemia

Blood pressure- the tension in the main arteries that is created by the beating of the heart and the resistance to flow and elasticity of the blood vessels

Blood transfusion- the transfer of blood or any of its parts to a person who has lost blood due to an injury, disease, or operation

Blood type- a category used to describe a person's blood according to the kinds of proteins present on the surface of the red blood cells

B lymphocyte- a type of white blood cell that makes antibodies and is an important part of the immune response

Boil- an inflamed, raised area of skin that is pus-filled; usually an infected hair follicle

Bone marrow- the fatty yellow or red tissue inside bones that is responsible for producing blood cells

Bone marrow transplant- a surgical procedure in which defective or cancerous bone marrow is replaced with healthy marrow, either from the patient or a donor

Bone spur- an abnormal growth of bone out of another bone, often located on the heel and usually painful

Booster- an additional dose of a vaccine taken after the first dose to maintain or renew the first one

Botulism- poisoning from poorly preserved food contaminated with a dangerous bacterial toxin that results in paralysis

Bowel- see Intestine

Bradycardia- a slow heart rate, usually below 60 beats per minute in adults

Brain damage- permanent death or damage of brain cells resulting in decreased mental ability

Brain death- the condition in which the brain stops functioning while the heart continues to beat

Breech birth- childbirth in which the baby is turned around in the uterus and emerges head-last instead of head-first

Bronchiolitis- an infection caused by a virus in the bronchioles (the smallest airways in the lungs), mainly affecting young children

Bronchitis- inflammation of the bronchial tubes, which connect the trachea to the lungs

Bronchoconstrictor- a substance that causes the lung airways to tighten up and become more narrow

Bronchodilator- a drug that widens the airways in the lungs to improve breathing; works by relieving muscle contraction or buildup of mucus

Bronchospasm- the temporary narrowing of the airways in the lungs, either as a result of muscle contraction or inflammation; may be caused by asthma, infection, lung disease, or an allergic reaction

Bruise- see Contusion

Bruxism- an unaware clenching or grinding of the teeth, usually during sleep

Bubonic plague- a form of plague in which lymph nodes in the groin and armpit swell

Bulimia- a disorder in which a person eats large amounts of food then forces vomiting or uses laxatives to prevent weight gain (called binging and purging)

Bunion- a hard, fluid-filled pad along the inside joint of the big toe; may be caused by wearing high-heeled shoes or a genetically weak joint

Burkitt's lymphoma- a cancer of lymph tissue that most frequently occurs in the abdomen, the ovaries, and the bones of the face; it is associated with malaria

Bursa- a fluid-filled sac that cushions and reduces friction in certain parts of the body

Bursitis- inflammation of a bursa due to excessive pressure or friction, or from injury

Butterfly bandage- a butterfly-shaped bandage that can help close a minor cut for proper healing

Bypass- a surgical technique in which the flow of blood or another body fluid is redirected around a blockage