Dictionary

pronator foot type A type of foot that rolls far inward during the weight-bearing phase of the stride. This type of foot is characterized by a very low or flat arch. Heavier people often have feet of this type.

pronucleus A cell nucleus with a haploid (halved) set of chromosomes—23 chromosomes in humans—that results from division (meiosis) of a germ cell. The male pronucleus is the sperm nucleus after it has entered the ovum at fertilization but before fusion with the female pronucleus. Similarly, the female pronucleus is the nucleus of the ovum before…

prophylactic 1 A medication or treatment given to prevent development of disease. 2 A drug or device for preventing pregnancy, particularly a condom.

prophylactic cranial irradiation Radiation therapy to the head that is intended to prevent cancer from spreading to the brain.

prophylaxis The prevention of disease.

propositus See proband.

proprioception The ability to sense stimuli arising within the body regarding position, motion, and equilibrium. Even if a person is blindfolded, he or she knows through proprioception if an arm is above the head or hanging by the side of the body. The sense of proprioception is disturbed in many neurological disorders. It can sometimes…

prospective study A study in which the subjects are first identified and then followed forward as time passes.

prostaglandin A hormone-like substance that participates in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure, modulation of inflammation, and production of the normal protective mucus lining of the stomach. Prostaglandins are derived from a chemical called arachidonic…

prostate acid phosphatase An enzyme that is produced by the prostate gland that is elevated in some patients with prostate cancer.

PRK Photorefractive keratectomy.

p.r.n. Pro re nata. Abbreviation meaning as needed. See also Appendix A, “Prescription Abbreviations.”