604 Introduction to Anatomy and Physiology
transfer RNA a molecule that binds to the
mRNA- ribosome complex and helps assemble amino
acids into polypeptides
transient ischemic attack (TIA) (is-KEE-mik) a
temporary lack of blood fl ow to the brain
transitional epithelium stratifi ed epithelium found in the
lining of hollow organs that can stretch
trans-unsaturated fats one category of unsaturated fatty
acids that are artifi cially produced; trans fats
transverse arch arch running sideways across the
bottom of the foot
transverse colon the mostly horizontal segment of the
colon between the ascending and descending colon
transverse plane an invisible, horizontal fl at surface that
divides the body into top and bottom halves
transverse plane movements rotational motions of the
body or body segments
transverse processes bony projections on the lateral
sides of the vertebral arches
traumatic brain injury mild or severe trauma that can
result from a violent impact to the head
tricuspid valve (trigh-KUS-pid) the valve that closes the
orifi ce between the right atrium and right ventricle of the
heart; composed of three cusps
triglycerides (trigh-GLIS-er-ighdz) compounds
composed of a glycerol molecule with three fatty acids
attached
trigone (TRIGH-gohn) the triangular region of the bladder
formed by the two ureteric orifi ces and the urethra
triiodothyronine (T3) (trigh-ah-doh-THAIR-oh-neen)
hormone found in thyroid hormone that is responsible
for controlling the rate of energy metabolism and heat
production; a more potent hormone than thyroxine
trophoblast cells (TROH-foh-blast) cells on the outer
layer of the blastocyst that nourish the embryo and aid in
implantation
tropic hormones (TROH-pik) pituitary hormones that act
on other endocrine glands; tropins
true ribs ribs having a bony articulation with the sternum
tuberculosis a highly contagious bacterial infection
caused by Myobacterium tuberculosis
tunica externa (TOO-ni-ka) the outermost layer of a
blood vessel composed mostly of fi brous connective
tissue that supports and protects the vessel
tunica intima (TOO-ni-ka) the innermost layer of a
blood vessel composed of a single layer of squamous
epithelial cells over a sheet of connective tissue; its smooth,
frictionless surface allows blood to fl ow smoothly through
the vessel
tunica media the thicker middle layer of a blood vessel
that contains smooth muscle cells, elastic fi bers, and
collagen; its muscle cells are directed by the sympathetic
nervous system to increase or decrease blood fl ow to
tissues as needed
tympanic cavity (tim-PAN-ik) see middle ear cavities
tympanic membrane (tim-PAN-ik) a sheet of tissue at
the end of the auditory canal; the eardrum
type I diabetes mellitus a form of insulin-dependent
diabetes in which the body produces an insuffi cient
amount of insulin or no insulin at all; juvenile-onset
diabetes
type II diabetes mellitus a form of diabetes (typically
non-insulin-dependent) that develops most often in
obese individuals and results from the body’s inability
to effi ciently move glucose from the bloodstream;
adult-onset diabetes
U
ulcer a break in the lining of the stomach, duodenum, or
lower esophagus
ulcerative colitis (koh-LIGH-tis) an infl ammatory bowel
disease that usually affects the colon and the mucosal
layer of the intestinal wall
ulna (UHL-nuh) larger bone of the lower arm
ulnar deviation rotation of the hand toward the little
fi nger
umami one of the fi ve basic tastes
umbilical cord the cord that connects the fetus to the
placenta
unicellular exocrine gland isolated secretory cells in an
epithelium
unipolar neurons nerve cells that have a single axon
with dendrites on the peripheral end and axon terminals
on the central end
universal donor a person with type O blood; type O
blood has no antigens that can be attacked by the host’s
blood, so it can be donated to anyone
universal recipient a person with type AB blood; type
AB blood has neither A nor B antibodies, so a universal
recipient can safely receive a transfusion of any blood
type
unsaturated term that describes fatty acids that have one
or more double bonds
upper extremity bones of the shoulders, arms, and
hands
upregulated increased
ureter (YOOR-eht-er) a duct through which urine travels
from the kidney to the bladder
ureteric orifi ces the two openings of the ureters into the
bladder; one opening lies at each corner of the trigone
urethra (yoo-REE-thra) a thin tube that connects the
urinary bladder to the outside environment
urinalysis laboratory analysis of urine to test for the
presence of disease
urinary bladder a hollow, muscular organ that stores
urine; bladder
urinary system the organs involved in the formation,
storage, and excretion of urine; includes the kidneys,
ureters, bladder, and urethra
urinary tract infection (UTI) an infection of the urethra,
bladder, ureters, and/or kidney, usually caused by
bacteria that enter the urethra at its outside opening
urine specifi c gravity the density (mass per unit volume)
of urine, divided by the density of pure water
urogenital diaphragm (yoor-oh-JEHN-i-tal) a double
layer of pelvic muscle that encircles the urethral
sphincters
uterine cycle the monthly cycle of changes that the
uterus undergoes; includes the menstrual, proliferative,
and secretory phases
uterine fi broids benign tumors of the muscular layer of
the uterus
uterine tubes (YOOT-er-in) tubes in which the oocyte is
fertilized; begin at the lateral end of the ovary and curve
up and around the ovary to terminate at the top lateral
portion of the uterus
uterus (YOOT-er-us) a hollow, muscular organ located in
front of the rectum and behind the bladder; the womb
uvula (YOO-vyoo-la) a fl eshy mass at the end of the oral
cavity that helps prevent food from entering the nasal
cavity