Glossary 601
semen the fl uid that contains sperm, which is delivered to
the female during intercourse; penile ejaculate
semicircular canals (SEHM-ee-SIR-kyoo-lar) inner
ear channels containing receptor hair cells that play an
important role in balance
semilunar valves (SEHM-ee-LOO-nar) valves situated
at the opening between the heart and the aorta and at
the opening between the heart and the pulmonary artery;
they prevent backfl ow of blood into the ventricles
seminal glands glands that produce up to 70% of the
volume of semen; seminal vesicles
seminal vesicles glands that produce up to 70% of the
volume of semen; seminal glands
seminiferous tubules small tubes in the testes in which
sperm form
sensory neurons transmitters that carry impulses from
the skin and organs to the spinal cord and brain; afferent
neurons
separase a protein that splits the sister chromatids by
cutting the centromeres in half
septum the structure made of cartilage that divides the
left and right air passages in the nose
serosa (seh-ROH-sa) the outermost layer of the
alimentary canal
serous fl uid a thin, clear liquid that serves as a lubricant
between parietal and visceral membranes
serous membranes (ser-us) thin sheets of tissues that
line body cavities that are closed to the outside world
sex hormones estrogens (female) and androgens (male)
sexual reproduction a method of reproduction that
involves two parents, with each parent contributing half
the genetic material for their offspring
sexually transmitted disease an infectious disease
transmitted through sexual contact; sexually transmitted
infection
shear a force that acts along a surface and perpendicular
to the length of a structure
shingles a disease that involves a painful, blistering rash
accompanied by headache, fever, and a general feeling
of unwellness; herpes zoster
shin splints the name for pain localized to the anterior
lower leg
short bones bones that are nearly cubicle in shape, such
as the bones of the wrist and ankle
shoulder complex all joints surrounding the shoulder,
including the acromioclavicular, sternoclavicular, and
glenohumeral joints
shoulder girdle bones surrounding the shoulder,
including the clavicle and scapula; pectoral girdle
sickle cell anemia a disease in which the red blood cells
are shaped like a sickle, or crescent, rather than a disk;
caused by irregularly shaped hemoglobin molecules in
the red blood cells
side bending movements within lateral fl exion
sigmoid colon (SIG-moyd) fi nal segment of the colon,
between the descending colon and the rectum
simple columnar epithelium epithelium with a single
layer of columnar cells
simple cuboidal epithelium epithelium with a single
layer of cuboidal cells
simple epithelia epithelium with a single layer of cells
simple squamous epithelium (SKWAH-mus) epithelium
with a single layer of fl attened cells
single nucleotide polymorphism base locations that
tend to vary; SNPs
sinoatrial node (SA node) (SIGH-noh-AY-tree-al) a small
mass of specialized tissue located in the right atrium that
normally acts as the pacemaker of the heart, causing it
to beat at a rate between 60 and 100 bpm; pacemaker
sinuses the air-fi lled cavities that surround the nose
sinusitis (SIGH-nus-IGH-tis) infl ammation of the sinuses
skeletal muscle voluntary muscle that is usually attached
to bone and helps us to move
skeletal physiology the study of how the skeleton
functions internally
skull the part of the skeleton composed of all of the
bones of the head
slow-twitch type of muscle that contracts slowly and is
fatigue resistant
small intestine the portion of the digestive tract where
most of the chemical breakdown of food, food absorption,
and water absorption occurs; the longest segment of the
GI tract
smooth ER a site where “replacement” membrane is
made for membranous structures in the cell
smooth muscle involuntary muscle found in the walls of
hollow organs
soft palate (PAL-at) the posterior part of the palate that
is made of muscle
somatic nervous system branch of the nervous system
that stimulates the skeletal muscles
somatic refl exes involuntary stimuli transmitted to
skeletal muscles from neural arcs in the spinal cord
sour one of the fi ve basic tastes
specifi c immune system see immune system
sperm (singular or plural) the male gamete; a haploid cell
that can fertilize an egg to make a zygote
spermatids (SPER-mat-ids) immature sperm cells
spermatogenesis (sper-mat-oh-JEHN-e-sis) sperm
formation
spermatogonia (sper-mat-oh-GOH-nee-a) stem cells
in the male that undergo mitosis; similar to oogonia in
females
sphenoidal sinuses (sfee-NOY-dal) two irregular cavities
in the body of the sphenoid bone that communicate with
the nasal cavities
sphenoid bone (SFEE-noyd) butterfl y shaped bone,
centrally located within the skull, that supports part of
the base of the brain, forms part of the orbits of the eyes,
and is connected to all of the other bones of the skull
sphincter pupillae (pyoo-PIL-ay) a muscle of the iris
which causes a contraction of the pupil in bright light
spinal cavity the internal opening that houses the
spinal cord
spinal cord a column of nerve tissue that extends from
the brain stem to the beginning of the lumbar region of
the spine
spinal nerves neural transmitters that branch from the
left and right sides of the spinal cord
spinous process bony projections on the posterior of
each vertebra
spirometer (spigh-RAHM-eh-ter) a device used for
measuring static lung volumes
spleen the largest lymphatic organ in the body, located
in the abdomen below the diaphragm; fi lters blood and
activates an immune response if necessary
spongy urethra the longest part of the male urethra
spontaneous abortion the naturally occurring premature
termination of pregnancy