Glossary 591
hypertension condition that occurs when the force of
blood against the arterial wall remains elevated for an
extended period of time; high blood pressure
hyperthyroidism a condition characterized by a visibly
enlarged thyroid gland in the neck; overactive thyroid
hypertrophy (high-PER-troh-fee) increase in bone
mineral density and strength
hyperventilation excessive ventilation that leads to an
abnormal expulsion of carbon dioxide
hypodermis the layer of skin beneath the dermis, which
serves as a storage repository for fat
hypothalamic inhibiting hormones hormones
secreted by the hypothalamus that direct the activities
of the pituitary gland; hypothalamic nonreleasing
hormones
hypothalamic nonreleasing hormones hormones
produced in the hypothalamus and carried by a vein to
the anterior pituitary, where they stop certain hormones
from being released; hypothalamic inhibiting hormones
hypothalamic releasing hormones hormones produced
in the hypothalamus and carried by a vein to the anterior
pituitary, where they stimulate the release of anterior
pituitary hormones
hypothalamus (HIGH-poh-THAL-a-mus) a portion
of the diencephalon and nervous system that is also
considered an endocrine gland; includes vital autonomic
regulatory centers that control functions such as
metabolism, heart rate, and blood pressure
hypothyroidism a condition caused by an underactive
thyroid gland
hypoxemia (HIGH-pahk-SEE-mee-a) a condition in which
arterial blood oxygen content is lowered
I
IgE antibody a class of antibody that interacts with
mast cells and basophils to cause histamine release,
infl ammation, and, sometimes, allergic reactions
ileocecal valve (IL-ee-oh-SEE-kal) valve located at
the end of the ileum that opens in response to gastrin
released by the stomach
ileum (IL-ee-um) longest and last portion of the
small intestine; between the jejunum and the large
intestine
iliac crest (IL-ee-ak) prominent upper edge of the ilium of
the hip bone
ilium (IL-ee-um) bone comprising most of each coxal bone,
connecting posteriorly to the sacrum at the sacroiliac joint
immune system the cells and chemicals that contribute
to the body’s specifi c defenses against disease
immunoglobulins (IM-yoo-noh-GLAHB-yoo-lins) proteins
that recognize particular antigens with great specifi city;
antibodies
immunotherapy a long-term, preventive treatment for
allergies; allergy shots
impetigo (IM-peh-TEE-goh) a bacterial infection common
in elementary school children that is characterized by
pink, blisterlike bumps, usually on the face
implantation the binding of the blastocyst to the
endometrium
incus see anvil
inferior term meaning below or under
inferior articular process indentation on the lower
side of each vertebra forming a facet joint with the next
vertebra
inferior concha (KAHN-ka) bones forming the sides of
the nasal cavity
inferior vena cava largest vein in the human body that
returns deoxygenated blood to the right atrium of the
heart from body regions below the diaphragm
infertility the inability of a couple to get pregnant
infl ammatory bowel disease a condition in which
the wall of the small and/or large intestine becomes
chronically infl amed
infl ammatory response physiological response to
tissue injury or infection including heat, redness, swelling,
and pain; infl ammation
infl uenza a viral infection that affects the respiratory
system; the fl u
infundibulum (in-fun-DI-byuh-lum) a short stalk on the
underside of the hypothalamus from which the pituitary
gland is suspended
ingestion the intake of food and liquids via the mouth
insertion muscle attachment to a bone that tends to
move when the muscle contracts
inspiration the process by which air fl ows into the lungs;
inhalation
inspiratory reserve volume (IRV) the amount of air that
can be inhaled immediately after a normal inhalation
insulin a hormone that promotes glucose uptake in body
tissues
insulin resistance a condition common in type II
diabetes in which the pancreas secretes insulin, but the
body’s insulin receptors are downregulated, causing low
blood glucose levels
integumentary system (in-TEHG-yoo-MEHN-ta-ree)
enveloping organ of the body that includes the epidermis,
dermis, sudoriferous and sebaceous glands; also
includes nails and hair
interatrial septum (IN-ter-AY-tree-al) the wall that
separates the right and left atria in the heart
interferons (IN-ter-FAIR-ahns) proteins released by cells
that have been infected with viruses; interfere with virus
reproduction
interleukins chemicals that stimulate an immune
response
intermediate fi lament a type of fi ber in the cytoskeleton,
made of keratin
internal respiration the process of gas exchange
between the tissues and arterial blood
internal urethral sphincter a layer of smooth muscle
located at the inferior end of the bladder and the proximal
end of the urethra; this muscle, which prohibits release of
urine, is under involuntary control
interneurons (inter-NOO-rahnz) nerve cells that form
bridges to transmit impulses between sensory and motor
neurons; association neurons
interosseus membrane (IN-ter-AHS-ee-es) tough,
fi brous connective tissue that bonds the radius and ulna
together and also binds the tibia and fi bula together
interphase the phase in the life cycle of a cell when it is
not dividing; DNA duplication occurs during this phase
interstitial fl uid (IN-ter-STISH-al) fl uid in the spaces
between cells
interstitial space the space between cells
interventricular septum (IN-ter-ven-TRIK-yoo-lar SEP-tum)
thick wall that divides the two ventricles in the heart
intervertebral discs (IN-ter-VER-teh-bral)
fi brocartilaginous cushions between vertebral bodies that
allow bending of the spine and help to create the normal
spinal curves
intestinal trunks lymphatic vessels that carry lymph from
abdominal organs toward the cisterna chyli