974
GLOSSARY
trachea
(tra
′
ke-ah)
Tubular organ that
leads from the larynx to the bronchi.
p. 742
transcellular fl
uid
(trans
″
sel
′
u-lar fl
oo
′
-
id) Part of the extracellular fl
uid,
including the fl
uid in special body
cavities. p. 811
transcription
(trans-krip
′
shun)
Manufacturing a complementary
RNA from DNA. p. 130
transcytosis
(trans
″
si-to
′
sis)
Combination of receptor-mediated
endocytosis and exocytosis that
moves particles through a cell.
p. 98
transfer RNA
(trans
′
fer RNA)
RNA
molecule that carries an amino acid
to a ribosome in protein synthesis;
tRNA. p. 131
translation
(trans-la
′
shun)
Assembly
of an amino acid chain according to
the sequence of base triplets in an
mRNA molecule. p. 131
transverse
(trans-vers
′
)
Plane that
divides a structure into superior and
inferior parts. p. 22
transverse colon
(trans-vers
′
ko
′
lon)
Part of the large intestine that extends
across the abdomen from right to left
below the stomach. p. 687
transverse tubule
(trans-vers
′
tu
′
bu
¯l)
Membranous channel that extends
inward from a muscle F
ber
membrane and passes through the
F ber. p. 288
triad
(tri
′
ad)
Group of three structures.
p. 288
tricuspid valve
(tri-kus
′
pid valv)
Heart
valve between the right atrium and
the right ventricle. p. 557
trigger zone
(trig
′
ger zo
¯n)
Sensitive
part of an axon where a nerve
impulse originates. p. 368
triglyceride
(tri-glis
′
er-ı¯d)
Lipid com-
posed of three fatty acids and a
glycerol molecule. p. 63
triiodothyronine
(tri
″
i-o
″
do-thi
′
ro-ne
¯n)
Type of thyroid hormone; T
3
.
p. 500
trisomy
(tri
′
so-me)
Condition in which
a cell has three chromosomes of a
particular type instead of two. p. 929
trochanter
(tro-kan
′
ter)
Broad process
on a bone. p. 208
trophoblast
(trof
′
o-blast)
Outer cells
of a blastocyst that give rise to cells
that become part of the placenta and
extraembryonic membranes. p. 880
tropic hormone
(tro
¯p
′
ik hor
′
mo
¯n)
Hormone that has an endocrine
gland as its target tissue. p. 492
tropomyosin
(tro
″
po-mi
′
o-sin)
Protein
that blocks muscle contraction until
calcium ions are present. p. 287
thrombin
(throm
′
bin)
Blood-clotting
enzyme that catalyzes formation of
F
brin from F
brinogen. p. 39
thrombocyte
(throm
′
bo-sı¯t)
Blood
platelet. p. 534
thrombocytopenia
(throm
″
bo-si
″
to-pe
′
ne-
ah)
Low number of platelets in the
circulating blood. p. 542
thromobopoietin
(throm
′
bo-poi
′
e
˘-tin)
A hormone that stimulates
megakaryocytes to differentiate from
hematopoietic stem cells. p. 534
thrombus
(throm
′
bus)
Blood clot that
remains where it forms in a blood
vessel. p. 541
thymosins
(thi
′
mo-sins)
Group of
peptides the thymus gland secretes
that increases production of certain
types of white blood cells. p. 512
thymus
(thi
′
mus)
Glandular organ in
the mediastinum, behind the sternum
and between the lungs. p. 512
thyroid gland
(thi
′
roid gland)
Endocrine
gland just below the larynx and in
front of the trachea that secretes
thyroid hormones. p. 499
thyroid-stimulating hormone
(thi
′
roid-
stim
″
u-la
¯t
′
eng hor
′
mo
¯n)
Hormone
secreted from the anterior pituitary
gland that controls secretion from
the thyroid gland; TSH. p. 496
thyroxine
(thi-rok
′
sin)
Hormone
secreted by the thyroid gland; T4.
p. 500
tidal volume
(tı¯d
′
al vol
′
u
¯m)
Volume of
air entering and leaving the lungs in
a respiratory cycle. p. 752
tissue
(tish
′
u)
Group of similar cells
that performs a specialized function.
p. 4
titin
(ti
′
tin)
Protein that attaches
myosin F
laments to z lines in
muscle. p. 287
T lymphocyte
(T lim
′
fo-sı¯t)
Type
of white blood cell that interacts
directly with antigen-bearing cells
and particles and secretes cytokines,
producing the cellular immune
response; T cell. p. 623
tonsil
(ton
′
sil)
Collection of lymphatic
tissue in the throat. p. 621
total lung capacity
(toh
′
tal lung kah-
pas
′
i-te)
Vital capacity plus
residual volume. p. 753
totipotent
(to-tip
′
o-tent)
Ability of a cell
to differentiate into any type of cell.
Only a fertilized ovum is totipotent.
p. 105
trabecula
(trah-bek
′
u-lah)
Branching
bony plate that separates irregular
spaces within spongy bone. p. 194
trace element
(tra
¯s el
′
e
˘-ment)
Basic
chemical substance needed in small
quantity. p. 52
systolic pressure
(sis-tol
′
ik presh
′
ur)
Arterial blood pressure reached
during the systolic phase of the
cardiac cycle. p. 580
T
tachycardia
(tak
″
e-kar
′
de-ah)
Abnormally rapid heartbeat. p. 572
tactile corpuscle
(tak
′
til kor
′
pus-l)
Sensory receptor close to the surface
of the skin that is sensitive to light
touch; Meissner’s corpuscle. p. 440
target cell
(tar
′
get sel)
Cell with speciF
c
receptors on which a hormone
exerts its effect. p. 16
tarsal
(tahr
′
sal)
Bone in the area
between the foot and leg. p. 24
tarsus
(tar
′
sus)
Ankle bones. p. 206
taste bud
(ta
¯st bud)
Organ containing
receptors associated with the sense
of taste. p. 448
telophase
(tel
′
o-fa
¯z)
Stage in mitosis
when newly formed cells separate.
p. 101
tendon
(ten
′
don)
Cordlike or bandlike
mass of white F
brous connective
tissue that connects a muscle to a
bone. p. 155
teratogen
(ter
′
ah-to-jen)
Chemical
or other environmental agent that
causes a birth defect. p. 892
testis
(tes
′
tis)
Primary male
reproductive organ; sperm cell-
producing organ (pl.,
testes
). p. 512
testosterone
(tes-tos
′
te
˘-ro
¯n)
Male sex
hormone secreted by the interstitial
cells of the testes. p. 833
tetanic contraction
(te
˘-tan
′
ik kon-
trak
′
shun)
Continuous, forceful
muscular contraction without
relaxation. p. 297
thalamus
(thal
′
ah-mus)
Mass of gray
matter at the base of the cerebrum
in the wall of the third ventricle.
p. 405
thermoreceptor
(ther
″
mo-re-sep
′
tor)
Sensory receptor sensitive to
temperature changes; heat and cold
receptors. p. 439
thiamine
(thi
′
ah-min)
Vitamin of the
B-complex group; vitamin B
1
. p. 713
thoracic
(tho-ras
′
ik)
Pertaining to the
chest. p. 12
thoracic cavity
(tho-ras
′
ik kav
′
i-te)
Hollow place in the chest. p. 12
threshold potential
(thresh
′
old po-
ten
′
shal)
Level of potential at
which an action potential or nerve
impulse is produced. p. 368
threshold stimulus
(thresh
′
old stim
′
u-lus)
Stimulation level that must be
exceeded to elicit a nerve impulse or
a muscle contraction. p. 296
