G-24 glossary
tubular secretion The step of urine formation in which
unwanted substances in peritubular capillaries are moved to
the urine forming in nephron tubules.
tumor A tissue mass composed of cells that are dividing at
an abnormally high rate.
tumor marker A substance that is produced by a specific
type of cancer cell or by normal cells in response to cancer.
tumor suppressor gene A gene whose protein product
operates to keep cell growth and division within nor-
mal bounds, or whose product has a role in keeping cells
anchored in place within a tissue.
tympanic membrane The eardrum, which vibrates when
struck by sound waves.
ulna One of two long bones of the forearm; the ulna extends
along the little finger side of the forearm, parallel to the
radius on the thumb side.
umbilical cord Structure containing blood vessels that
connect a fetus to its mother’s circulatory system by way of
the placenta.
urea The main nitrogen-containing waste product when cells
break down proteins.
ureter Channel that carries urine from each kidney to the
urinary bladder.
urethra Tube that carries urine outside the body from the
bladder.
urinary bladder Hollow organ that stores urine.
urinary excretion A mechanism by which excess water and
solutes are removed by way of the urinary system.
urine Fluid formed by filtration, reabsorption, and secretion
in kidneys; consists of wastes, excess water, and unneeded
solutes.
uterus (you-tur-us) [L. uterus, womb] Chamber in which
the developing embryo is contained and nurtured during
pregnancy.
vaccine Antigen-containing preparation injected into the
body or taken orally; it elicits an immune response leading to
the proliferation of memory cells that offer long-lasting pro-
tection against that particular antigen.
vagina Chamber of the female reproductive system that
receives the male penis and sperm, forms part of the birth
canal, and channels menstrual flow to the exterior.
variable In a scientific experiment, the only factor that is
not the same in the experimental group as it is in the control
group.
vas deferens Tube leading to the ejaculatory duct; one of
several tubes through which sperm move after they leave the
testes just prior to ejaculation.
vasoconstriction Decrease in the diameter of an arteriole, so
that blood pressure rises; may be triggered by the hormones
epinephrine and angiotensin.
vasodilation Enlargement of arteriole diameter, so that blood
pressure falls; may be triggered by hormones including epi-
nephrine and angiotensin.thyroid gland An endocrine gland that produces hormones
that affect overall metabolic rates, growth, and development.
tidal volume Volume of air, about 500 milliliters, that enters
or leaves the lungs in a normal breath.
tight junction Cell junction where strands of fibrous proteins
collectively block leaks between the adjoining cells.
tissue A group of cells and intercellular substances that func-
tion together in one or more specialized tasks.
tonicity The relative concentrations of solutes in two fluids,
such as inside and outside a cell. When solute concentrations
are isotonic (equal in both fluids), water shows no net osmotic
movement in either direction. When one fluid is hypotonic
(has less solutes than the other), the other is hypertonic (has
more solutes) and is the direction in which water tends to
move.
total fertility rate (TFR) The average number of children
born to the women in a given population during their repro-
ductive years.
trace element Any element that represents less than
0.01 percent of body weight.
tracer A substance with a radioisotope attached to it so that
its pathway or destination in a cell, organism, ecosystem, or
some other system can be tracked, as by scintillation counters
that detect its emissions.
trachea (tray-kee-uh) The windpipe, which carries air
between the larynx and bronchi.
transcription [L. trans, across, and scribere, to write] Of
protein synthesis, the assembly of an RNA strand on one of
the two strands of a DNA double helix; the base sequence of
the resulting transcript is complementary to the DNA region
on which it was assembled.
transfer RNA (tRNA) Of protein synthesis, any of the type of
RNA molecules that bind and deliver specific amino acids to
ribosomes and pair with mRNA code words for those amino
acids.
translation In protein synthesis, the conversion of the coded
sequence of information in mRNA into a particular sequence
of amino acids to form a polypeptide chain; depends on inter-
actions of rRNA, tRNA, and mRNA.
translocation A change in a chromosome’s structure
following the insertion of part of a nonhomologous
chromosome into it.
transporter protein One of many kinds of membrane pro-
teins involved in active or passive transport of substances
across the lipid bilayer of a plasma membrane. Solutes on one
side of the membrane pass through the protein’s interior to
the other side.
triglyceride (neutral fat) A lipid having three fatty acid tails
attached to a glycerol backbone. Triglycerides are the body’s
most abundant lipids and richest energy source.
tRNA See transfer RNA.
tubular reabsorption In the kidney, the diffusion or active
transport of water and usable solutes out of a nephron and
into capillaries leading back to the general circulation; regu-
lated by ADH and aldosterone.
Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).