Progesterone (pro-JES-te-ron) A female sex hormone produced by
the ovaries that helps prepare the endometrium of the uterus for
implantation of a fertilized ovum and the mammary glands for
Prognosis (prog-NO-sis) A forecast of the probable results of a disor-
der; the outlook for recovery.
Prolactin (PRL) (pro-LAK-tin) A hormone secreted by the anterior
pituitary that initiates and maintains milk secretion by the mam-
Prolapse (PRO-laps) A dropping or falling down of an organ, espe-
cially the uterus or rectum.
Proliferation (pro-lif'-er-A-shun) Rapid and repeated reproduction of
new parts, especially cells.
Pronation (pro-NA-shun) A movement of the forearm in which the
palm is turned posteriorly.
Prophase (PRO-faz) The first stage of mitosis during which chromatid
pairs are formed and aggregate around the metaphase plate of
Proprioception (pro-pre-o-SEP-shun) The perception of the position of
body parts, especially the limbs, independent of vision; this sense
is possible due to nerve impulses generated by proprioceptors.
Proprioceptor (pro'-pre-o-SEP-tor) A receptor located in muscles,
tendons, joints, or the internal ear (muscle spindles, tendon
organs, joint kinesthetic receptors, and hair cells of the vestibular
apparatus) that provides information about body position and
Prostaglandin (PG) (pros'-ta-GLAN-din) A membrane-associated lipid;
released in small quantities and acts as a local hormone.
Prostate (PROS-tat) A doughnut-shaped gland inferior to the urinary
bladder that surrounds the superior portion of the male urethra
and secretes a slightly acidic solution that contributes to sperm
motility and viability.
Protein An organic compound consisting of carbon, hydrogen,
oxygen, nitrogen, and sometimes sulfur and phosphorus; syn-
thesized on ribosomes and made up of amino acids linked by
Proteasome (PRO-te-a-som) Tiny cellular organelle in the cytosol and
nucleus containing proteases that destroy unneeded, damaged,
or faulty proteins.
Prothrombin (pro-THROM-bin) An inactive blood-clotting factor syn-
thesized by the liver, released into the blood, and converted to
active thrombin in the process of blood clotting by the activated
Protraction (pro-TRAK-shun) The movement of the mandible or
clavicle forward on a plane parallel with the ground.
Proximal (PROK-si-mal) Nearer the attachment of a limb to the trunk;
nearer to the point of origin or attachment.
Pseudopods (SOO-do-pods) Temporary protrusions of the leading
edge of a migrating cell; cellular projections that surround a par-
ticle undergoing phagocytosis.
Ptosis (TO-sis) Drooping, as of the eyelid or the kidney.
Puberty (PO-ber-te) The time of life during which the secondary
sex characteristics begin to appear and the capability for sexual
reproduction is possible; usually occurs between the ages of 10
Pubic symphysis (SIM-fi-sis) A slightly movable cartilaginous joint
between the anterior surfaces of the hip bones.
Puerperium (pu'-er-PER-e-um) The period immediately after child-
birth, usually 4-6 weeks.
Pulmonary (PUL-mo-ner'-e) Concerning or affected by the lungs.
Pulmonary circulation The flow of deoxygenated blood from the
right ventricle to the lungs and the return of oxygenated blood
from the lungs to the left atrium.
Pulmonary edema (e-DE-ma) An abnormal accumulation of inter-
stitial fluid in the tissue spaces and alveoli of the lungs due to
increased pulmonary capillary permeability or increased pulmo-
nary capillary pressure.
Pulmonary embolism (PE) (EM-bo-lizm) The presence of a blood clot
or a foreign substance in a pulmonary arterial blood vessel that
obstructs circulation to lung tissue.
Pulmonary ventilation (ven-ti-LA-shun) The inflow (inhalation) and
outflow (exhalation) of air between the atmosphere and the
lungs. Also called breathing.
Pulp cavity A cavity within the crown and neck of a tooth, which
is filled with pulp, a connective tissue containing blood vessels,
nerves, and lymphatic vessels.
Pulse (POLS) The rhythmic expansion and elastic recoil of a systemic
artery after each contraction of the left ventricle.
Pupil The hole in the center of the iris, the area through which light
enters the posterior cavity of the eyeball.
Purkinje fiber (pur-KIN-je) Muscle fiber (cell) in the ventricular tissue
of the heart specialized for conducting an action potential to the
myocardium; part of the conduction system of the heart.
Pus The liquid product of inflammation containing leukocytes or
their remains and debris of dead cells.
Pyloric sphincter (pr-LOR-ik) A thickened ring of smooth muscle
through which the pylorus of the stomach communicates with
the duodenum. Also called the pyloric valve.
Pyramid (PIR-a-mid) A pointed or cone-shaped structure. One of
two roughly triangular structures on the anterior aspect of the
medulla oblongata composed of the largest motor tracts that run
from the cerebral cortex to the spinal cord. A triangular structure
in the renal medulla.
Pyramidal tracts (pathways) (pi-RAM-i-dal)
S e e
Direct motor path-
QRS wave The deflection wave of an electrocardiogram that repre-
sents the onset of ventricular depolarization.
Quadriplegia (kwod'-ri-PLE-je-a) Paralysis of four limbs: two upper
and two lower.
Radiographic anatomy (ra'-de-o-GRAF-ic) Diagnostic branch of
anatomy that includes the use of x rays.
Rapid eye movement (REM) sleep Stage of sleep in which dreaming
occurs, lasting for 5 to 10 minutes several times during a sleep