965
GLOSSARY
secretes that affects electrolyte
concentrations in body fl
uids. p. 506
mitochondrion
(mi
to-kon
dre-on)
Organelle housing enzymes that
catalyze aerobic reactions of cellular
respiration (pl.,
mitochondria
). p. 83
mitosis
(mi-to
sis)
Division of a
somatic cell, forming two genetically
identical cells. p. 100
mitral valve
(mi
tral valv)
Heart valve
located between the left atrium and
the left ventricle; bicuspid valve.
p. 557
mixed nerve
(mikst nerv)
Nerve that
includes both sensory and motor
nerve F
bers. p. 412
molar
(mo
lar)
Rear tooth with a
fl attened surface adapted for
grinding food. p. 659
molecular formula
(mo-lek
u-lar for
mu-
lah)
Abbreviation for the number
of atoms of each element in a
compound. p. 53
molecule
(mol
e
˘-ku
¯l)
Particle composed
of two or more joined atoms. p. 4
monoamine oxidase
(mon
o-am
e
¯n ok
sı˘-
da
¯s)
Enzyme that catalyzes the
removal of an amine group from a
compound. p. 374
monocyte
(mon
o-sı¯t)
Type of white
blood cell that is a phagocyte.
p. 532
monosaccharide
(mon
o-sak
ah-rı¯d)
Single sugar, such as glucose or
fructose. p. 62
monosomy
(mon
o-so
me)
Cell missing
one chromosome. p. 929
morula
(mor
u-lah)
Early stage in
prenatal development; solid ball of
cells. p. 879
motor area
(mo
tor a
re-ah)
Region
of the brain that sends impulses to
muscles or glands. p. 402
motor end plate
(mo
tor end pla
¯t)
Specialized part of a muscle F
ber
membrane at a neuromuscular
junction. p. 290
motor nerve
(mo
tor nerv)
Nerve that
consists of motor nerve F bers. p. 412
motor neuron
(mo
tor nu
ron)
Neuron
that transmits impulses from the
central nervous system to an
effector. p. 289
motor unit
(mo
tor unit)
A motor
neuron and its associated muscle
F bers. p. 290
mucosa
(mu-ko
sah)
Innermost layer of
the alimentary canal. p. 653
mucous membrane
(mu
kus mem
bra
¯n)
Membrane that lines tubes and body
cavities that open to the outside of
the body. p. 163
mucus
(mu
kus)
±luid secretion of
mucous cells. p. 152
menses
(men
se
¯z)
Shedding of blood
and tissue from the uterine lining
at the end of a female reproductive
cycle. p. 859
mental
(men
tal)
Pertaining to the
mind; pertaining to the chin body
region. p. 23
merocrine gland
(mer
o-krı˘n gland)
A structure whose cells remain
intact while secreting. p. 150
mesentery
(mes
en-ter
e)
±old of
peritoneal membrane that attaches
an abdominal organ to the
abdominal wall. p. 680
mesoderm
(mez
o-derm)
Middle primary
germ layer of the embryo. p. 885
messenger RNA
(mes
in-jer RNA)
RNA
that transmits information for a
protein
s amino acid sequence
from the nucleus of a cell to the
cytoplasm; mRNA. p. 130
metabolic pathway
(met
ah-bol
ik
path
wa)
Series of linked,
enzymatically controlled chemical
reactions. p. 118
metabolism
(me
˘-tab
o-lizm)
The
chemical reactions in cells that use
or release energy. p. 6
metacarpal
(met
ah-kar
pal)
Bone of
the hand between the wrist and
F nger bones. p. 229
metaphase
(met
ah-fa
¯z)
Stage in
mitosis when chromosomes align in
the middle of the cell p. 101
metatarsal
(met
ah-tar
sal)
±oot bone
between the ankle and toe bones.
p. 236
microF
lament
(mi
kro-F l
ah-ment)
Rod
of the protein actin that provides
structural support or motility in the
cytoplasm. p. 88
microglia
(mi-krog
le-a)
Neuroglia that
support neurons and phagocytize.
p. 363
micronutrient
(mi-kro-nu
tre-ent)
Nutrient (vitamin or mineral)
required in small amount. p. 699
microtubule
(mi
kro-tu
bu
¯l)
Hollow
rod of the protein tubulin in the
cytoplasm. p. 88
microvillus
(mi
kro-vil
us)
Cylindrical
process that extends from some
epithelial cell membranes and
increases the membrane surface area
(pl.
, microvilli
). p. 681
micturition
(mik
tu-rish
un)
Urination.
p. 802
midbrain
(mid
bra
¯n)
Small region
of the brainstem between the
diencephalon and the pons. p. 398
mineral
(min
er-al)
Inorganic element
essential in human metabolism. p. 717
mineralocorticoid
(min
er-al-o-kor
tı˘-
koid)
Hormone the adrenal cortex
mechanoreceptor
(mek
ah-no-re-
sep
tor) Sensory receptor sensitive
to mechanical stimulation, such as
changes in pressure or tension.
p. 439
medial
(me
de-al)
Toward or near the
midline. p. 21
mediastinum
(me
de-ah-sti
num)
Tissues and organs of the thoracic
cavity that form a septum between
the lungs. p. 12
medulla
(me
˘-dul
ah)
Inner portion of
an organ. p. 504
medulla oblongata
(me
˘-dul
ah ob
long-
gah
tah)
Part of the brainstem
between the pons and the spinal
cord. p. 408
medullary cavity
(med
u-la
¯r
e kav
ı˘-te)
Cavity containing marrow in the
diaphysis of a long bone. p. 194
medullary respiratory center
(med
u-
la
¯r
e re-spi
rah-to
re sen
ter)
Area
of the brainstem that controls the
rate and depth of breathing. p. 756
megakaryocyte
(meg
ah-kar
e-o-sı¯t)
Large bone marrow cell that shatters
to yield blood platelets. p. 526
meiosis
(mi-o
sis)
Cell division that
halves the genetic material, resulting
in egg and sperm cells (gametes).
p. 100
melanin
(mel
ah-nin)
Dark pigment in
skin and hair. p. 174
melanocyte
(mel
ah-no-sı¯t)
Melanin-
producing cell. p. 174
melatonin
(mel
ah-to
nin)
Hormone
that the pineal gland secretes. p. 512
membrane potential
(mem
bra
¯n po-
ten
shal)
Unequal distribution of
positive and negative ions on two
sides of a membrane. p. 366
memory cell
(mem
o-re sel)
B lympho-
cyte or T lymphocyte produced in
a primary immune response that
can be activated rapidly if the same
antigen is encountered in the future.
p. 632
memory consolidation
(mem
o-re kon-
sol
ı˘-da
shun)
Conversion of
short-term memories to long-term
memories. p. 404
menarche
(me
˘-nar
ke)
±irst menstrual
period. p. 857
meninx
(me
-ninks)
Membrane that
covers the brain and spinal cord (pl.,
meninges
). p. 265
meniscus
(men-is
kus)
±ibrocartilage
that separates the articulating
surfaces of bones in the knee (pl.,
menisci
). p. 265
menopause
(men
o-pawz)
Cessation of
the female reproductive cycle.
p. 860
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