Medical Dictionary: B

B cell: A type of lymphocyte (white blood cell). B cells, together with T cells, are the “big guns” of the immune system response to an invasion by a foreign molecule.

bariatric surgery: One of several gastrointestinal operations that cause therapeutic weight loss.

basilar artery: The artery that supplies blood to the cerebellum, the brainstem, and the back of the brain.

benign prostatic hyperplasia (BPH): A noncancerous enlargement of the prostate that can interfere with urination.

benign: Not cancerous.

benzodiazepines: Medications that work by attaching to benzodiazepine-GABA receptors, helping to maintain levels of the neurotransmitter GABA in the brain.

beta blockers: Medications used to treat a variety of illnesses, including heart disease, high blood pressure, and migraine headaches. They function in exactly the opposite way from beta-2 agonists. They can worsen asthma control and cause asthma flare-ups.

beta carotene: A precursor that is converted by the body into vitamin A. Beta carotene acts as an antioxidant. It’s found in many green vegetables and dark yellow or deep orange fruits and vegetables.

beta cells: Cells that make and secrete insulin; located in the islets of Langerhans of the pancreas.

beta-agonists: Members of one family of bronchodilator medicines. Beta-2 agonist drugs share a similar chemical structure and a common mechanism of action. They are all related to adrenaline (epinephrine).

bile: Fluid secreted by the liver that helps break down fats in the small intestine.

bioavailability: How quickly and completely a nutrient can be absorbed and used by the body.

biofeedback: A therapy that uses specialized devices to help individuals learn how to influence the function of organs or body systems that aren’t usually thought to be under conscious control.

biological variability: Fluctuations that occur naturally over time in the levels of a substance such as cholesterol in a person’s body.

biopsy: A procedure in which tissue or cells are removed from the body and examined microscopically to determine whether cancer is present.

bisphosphonates: A class of compounds, including alendronate and risedronate, that slow bone resorption. These medications are used to prevent and treat osteoporosis.

bitter: Botanical medicine with a bitter taste that is traditionally believed to aid the digestive process.

bladder neck: The junction of the bladder and the urethra.

blepharoplasty (eyelid surgery): Surgical removal of fat, excess skin, bags, pouches, and wrinkles in the upper or lower eyelids.

blister: A fluid-filled sac that develops between layers of skin, usually after prolonged irritation from an external source, like a shoe or the ground.

blood urea nitrogen (BUN) test: A test that measures levels of urea in your blood to assess how well your kidneys are functioning.

body mass index (BMI): An estimate of an individual’s relative body fat calculated from his or her height and weight.

bone mass: The total amount of bone tissue in the body.

bone mineral density (BMD): The amount of mineralized bone tissue in a given area, usually calculated in grams per square centimeter.

bone scan: A diagnostic procedure in which radioactive material is injected into the patient’s bloodstream to produce images of the bony skeleton. Used to locate areas of rapid bone formation that might signal, for example, a tumor or an infection.

Botox: Brand name for a substance made of botulinum toxin type A that eases the appearance of some facial wrinkles by relaxing the underlying muscles.

Bouchard’s nodes: bony nodules that may form in the middle joints of one or more fingers in people with osteoarthritis.

brachytherapy: Treatment using seeds or pellets of radioactive material, which are implanted in the prostate to destroy cancer cells.

brain imaging: A variety of technologies, such as computed tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), and positron emission tomography (PET), used to examine the structure or function of different regions of the brain.

brainstem: The brain structure that is the major communication route among the brain, spinal cord, and peripheral nerves; controls heart rate, breathing, and other vital functions.

breast augmentation: Insertion of implants to enlarge the size of the breasts.

breath focus: A form of meditation that elicits the relaxation response; breath focus relies on deep, even breathing, a passive attitude, and a focus word or focal point.

bronchial tubes: The system of branching tubes that carries air through the lungs to the tiny air sacs of the lungs. There, oxygen can be passed into the blood and carbon dioxide released to the air.

bronchodilator: A type of medication that acts to open the breathing passages primarily by relaxing the muscles surrounding the bronchial tubes.

bunion: An angular deformity of the big toe, causing a bump to develop at its base; may become inflamed and painful.

bunionette: A condition similar to a bunion, but affecting the base of the fifth toe.

bursae: Cushioning sacs containing lubricating fluid located at a point of friction between two moving structures, such as a muscle and a tendon.

bursitis: Inflammation of the bursae, fluid-filled sacs that ease friction between tendons and bones (and tendons and ligaments), causing swelling and pain.