Bolus (BO-lus) A soft, rounded mass, usually food, that is swallowed.
Brachial plexus (BRA-ke-al PLEK-sus) A network of nerve axons of the
ventral rami of spinal nerves C5, C6, C7, C8, and T1. The nerves
that emerge from the brachial plexus supply the upper limb.
Bradycardia (brad'-i-KAR-de-a) A slow resting heart or pulse rate
(under 50 beats per minute).
Brain The part of the central nervous system contained within the
Brain stem The portion of the brain immediately superior to the spi-
nal cord, made up of the medulla oblongata, pons, and midbrain.
Brain waves Electrical signals that can be recorded from the skin of
the head due to electrical activity of brain neurons.
Broca’s area (BRO-kaz) Motor area of the brain in the frontal lobe that
translates thoughts into speech. Also called the motor speech area.
Bronchi (BRONG-kT) Branches of the respiratory passageway includ-
ing primary bronchi (the two divisions of the trachea), second-
ary or lobar bronchi (divisions of the primary bronchi that are
distributed to the lobes of the lungs), and tertiary or segmental
bronchi (divisions of the secondary bronchi that are distributed to
bronchopulmonary segments of the lungs).
S in g u la r
Bronchial tree The trachea, bronchi, and their branching structures
up to and including the terminal bronchioles.
Bronchiole (BRONG-ke-ol) Branch of a tertiary bronchus further divid-
ing into terminal bronchioles (distributed to lobules of the lungs),
which divide into respiratory bronchioles (distributed to alveolar
Bronchitis (brong-KT-tis) Inflammation of the mucous membrane of
the bronchial tree; characterized by hypertrophy and hyperplasia
of seromucous glands and goblet cells that line the bronchi and
which results in a productive cough.
Buccal (BUK-al) Pertaining to the cheek or mouth.
Buffer system (BUF-er) A pair of chemicals—one a weak acid and the
other the salt of the weak acid, which functions as a weak base—
that resists changes in pH.
Bulbourethral gland (bul'-bo-u-RE-thral) One of a pair of glands
located inferior to the prostate on either side of the urethra that
secretes an alkaline fluid into the urethra. Also called a Cowper's
boo-LE-me-a) A disorder characterized by
overeating at least twice a week followed by purging by self-
induced vomiting, strict dieting or fasting, vigorous exercise, or
use of laxatives or diuretics. Also called binge-purge syndrome.
Bulk flow The movement of large numbers of ions, molecules,
or particles in the same direction due to pressure differences
(osmotic, hydrostatic, or air pressure).
Bulk-phase endocytosis (pi'-no-sT-TO-sis) A process by which most
body cells can ingest membrane-surrounded droplets of intersti-
Bundle branch One of the two branches of the atrioventricular (AV)
bundle made up of specialized muscle fibers (cells) that transmit
electrical impulses to the ventricles.
Bursa (BUR-sa) A sac or pouch of synovial fluid located at friction
points, especially about joints.
Buttocks (BUT-oks) The two fleshy masses on the posterior aspect of
the inferior trunk, formed by the gluteal muscles.
Calcaneal tendon (kal-KA-ne-al) The tendon of the soleus, gastroc-
nemius, and plantaris muscles at the back of the heel. Also called
the Achilles tendon (a-KIL-ez).
Calcification (kal-si-fi-KA-shun) Deposition of mineral salts, primarily
hydroxyapatite, in a framework formed by collagen fibers in which
the tissue hardens. Also called mineralization (min'-e-ral-i-ZA-shun).
Calcitonin (CT) (kal-si-TO-nin) A hormone produced by the parafollicu-
lar cells of the thyroid gland that can lower the amount of blood
calcium and phosphates by inhibiting bone resorption (break-
down of bone extracellular matrix) and by accelerating uptake of
calcium and phosphates into bone extracellular matrix.
Calculus (KAL-ku-lus) A stone, or insoluble mass of crystallized salts
or other material, formed within the body, as in the gallbladder,
kidney, or urinary bladder.
Callus (KAL-lus) A growth of new bone tissue in and around a frac-
tured area, ultimately replaced by mature bone. An acquired,
Calorie (KAL-o-re) A unit of heat. A calorie (cal) is the standard unit
and is the amount of heat needed to raise the temperature of 1
water from 14 °C to 15 °C. The kilocalorie (kcal) or Calorie (spelled
with an uppercase C), used to express the caloric value of foods
and to measure metabolic rate, is equal to 1000 cal.
Calyx (KAL-iks) Any cuplike division of the kidney pelvis.
P lu r a l is
Canal (ka-NAL) A narrow tube, channel, or passageway.
Canaliculus (kan'-a-LIK-u-lus) A small channel or canal, as in bones,
where they connect lacunae.
P lu r a l is
Cancellous (KAN-sel-us) Having a reticular or latticework structure,
as in spongy bone tissue.
Capacitation (ka'-pas-i-TA-shun) The functional changes that sperm
undergo in the female reproductive tract that allow them to fertil-
ize a secondary oocyte.
Capillary (KAP-i-lar'-e) A microscopic blood vessel located between
an arteriole and venule through which materials are exchanged
between blood and interstitial fluid.
Carbohydrate (kar'-bo-HT-drat) An organic compound containing car-
bon, hydrogen, and oxygen in a particular amount and arrange-
ment and composed of monosaccharide subunits; usually has the
general formula (CH2O)n.
Carcinogen (kar-SIN-o-jen) A chemical substance or radiation that
Cardiac arrest (KAR-de-ak) Cessation of an effective heartbeat in
which the heart is completely stopped or in ventricular fibrillation.
Cardiac cycle A complete heartbeat consisting of systole (contrac-
tion) and diastole (relaxation) of both atria plus systole and
diastole of both ventricles.
Cardiac muscle Striated muscle fibers (cells) that form the wall of the
heart; stimulated by an intrinsic conduction system and regu-
lated by autonomic motor neurons.