586 Introduction to Anatomy and Physiology
diastole (digh-AS-toh-lee) the period of relaxation in the
heart when the chambers are fi lling with blood
diencephalon (DIGH-ehn-SEHF-a-lahn) area of the brain
that includes the epithalamus, thalamus, metathalamus,
and hypothalamus; the interbrain
differentiate to divide by mitosis to form specialized
daughter cells
diffusion the movement of material from where it is
concentrated to where it is less concentrated
dilation the stage of labor during which the opening of
the cervix dilates, or widens
dilator pupillae a muscle of the iris that causes
enlargement of the pupil in the presence of dim light
diploid (DIP-loyd) a cell having two sets of chromosomes:
one set from the mother and one set from the father
diplopia (di-PLOH-pee-a) the condition that occurs when
one eye is misaligned; double vision
dislocation injury involving displacement of a bone from
its joint socket
distal convoluted tubule the last part of a nephron
through which urine fl ows before reaching the collecting
duct; some minerals and nutrients are reabsorbed from
urine, and some waste products are secreted into urine,
through this tubule
distal radioulnar joint (RAY-dee-oh-UHL-nar) joint
between the radius and ulna that is close to the wrist
diuresis (DIGH-yoo-REE-sis) urine excretion
diuretics chemicals that stimulate urine production to
decrease fl uid retention in the body
DNA a polymer of nucleotides with the bases adenosine,
guanine, cytosine, and thymine; deoxyribonucleic acid
dorsal ramus (DOR-sal RAY-mus) the division of
posterior spinal nerves that transmit motor impulses to
the posterior trunk muscles and relay sensory impulses
from the skin of the back
dorsifl exion (DOR-si-FLEHK-shun) movement of the top
of the foot toward the lower leg
downregulated decreased
dry macular degeneration a condition caused by
progressive thinning of the retina
ductus arteriosus (ar-tair-ee-OH-sus) a short, broad
vessel in the fetus that connects the left pulmonary artery
with the descending aorta, allowing most of the blood to
bypass the infant’s lungs
ductus deferens the secretory duct of the testis, which
extends from the epididymis and joins with the excretory
duct of the seminal gland; vas deferens
duodenum (DOO-ah-DEH-num) fi rst segment of the
small intestine, which is located between the pyloric
valve of the stomach and the jejunum
dura mater (DOO-rah MAY-ter) the tough, outer
membrane of the brain and spinal cord
dwarfi sm a condition in which the pituitary gland hypo-
secretes growth hormone, resulting in an adult height of
less than four feet
dynamic lung volume lung volume measurements that
also measure the rate of fl ow
E
eardrum see tympanic membrane
earwax see cerumen
eccentric (ehk-SEHN-trik) a type of contraction that
causes lengthening of a muscle
eccrine glands (EK-rin) the major sweat glands of the
body
ectopic pregnancy the implantation and development of
a fertilized egg in the pelvic cavity or uterine tube, rather
than in the uterus
effector unit that receives a command stimulus from the
control center and causes an action to help maintain
homeostasis
effector cells short-lived cells that fi ght an infectious
invader
efferent lymphatic vessel vessel that carries lymph out
of a lymph node
efferent nerves motor transmitters that carry impulses
from the central nervous system out to the muscles and
glands
efferent pathway the route on which a command
stimulus travels from the control center to an effector
ejaculation the discharge of sperm from the ejaculatory
duct during the male sexual response
ejaculatory duct the duct through which sperm is carried
elastic a response that occurs when force is removed
and the structure returns to its original size and shape
elastic cartilage type of cartilage with many elastic fi bers
elastic fi bers fi bers of the cytoskeleton that can lengthen
when stretched and spring back to their original length
when released
elasticity the ability of a material to spring back to its
original shape after being stretched
elastic limit the stretch point beyond which a tissue can
no longer return to its original size and shape
electrical synapse site where communication occurs
between cells through direct transfer of electrical charges
electrocardiogram (ee-LEHK-troh-KAHR-dee-oh-gram)
a recording of the electrical activity of the heart; ECG
electrochemical event activity involving conversion of an
electrical charge into chemical messengers; an example
is the transmission of nerve impulses
embryo the developing human from the time of
implantation to the end of the eighth week after
conception
emphysema (EHM-fi -SEE-ma) chronic infl ammation of
the lungs characterized by an abnormal increase in the
air spaces near the bronchioles; causes an accumulation
of carbon dioxide in the lungs
emulsifi cation the breakdown of large fat particles into
much smaller particles, aided by bile
enamel the substance that forms the coating of each
tooth; the hardest material in the body
endocarditis (EHN-doh-kahr-DIGH-tis) infl ammation
of the innermost lining of the heart, including the inner
surface of the chambers and the valves
endocardium (EHN-doh-KAHR-dee-um) the innermost
layer of the heart, which lines the interior of the heart
chambers and covers the valves of the heart
endocrine gland a gland that secretes its product into
the interstitial space
endolymph (EHN-doh-limf) a thick fl uid inside the
membranous labyrinth
endometriosis (EHN-doh-MEE-tree-OH-sis) an
abnormal condition in which endometrial cells (cells
of the uterine lining) grow outside the uterus, often
producing pain and sometimes resulting in infertility
endometrium (ehn-doh-MEE-tree-um) the mucous
membrane that forms the innermost layer of the uterus
endomysium (EHN-doh-MIZ-ee-um) a fi ne, protective
sheath of connective tissue around a skeletal muscle fi ber
endoneurium (EHN-doh-NOO-ree-um) a delicate,
connective tissue that surrounds each nerve fi ber