Pacemaker  - an electronic device that is surgically implanted into the patient's heart and chest to regulate heartbeat.

Pain threshold - the point at which a stimulus causes a feeling of pain.

Palliative treatment - therapy that relieves symptoms, such as pain, but does not alter the course of the disease; its primary purpose is to improve the quality of life.

Pallidotomy - a surgical procedure in which a part of the brain, called the globus pallidus, is lesioned in order to improve symptoms of tremor, rigidity, and bradykinesia.

Palming - an imaging technique involving the visualization of color.

Palpitation - sensation of rapid heartbeats.

Palsy - paralysis of a muscle or group of muscles.

Pancreas - long gland that lies behind the stomach; manufactures insulin and digestive enzymes.

Papillary stenosis - condition in which the openings of the bile ducts and pancreatic ducts narrow.

Parietal cells - cells in the stomach wall that make hydrochloric acid.

Parkinsonism - the name given to a group of disorders with similar features including four primary symptoms: tremor, rigidity, postural instability, and bradykinesia, that are the result of the loss of dopamine-producing brain cells.

Parosmia - any disease or perversion of the sense of smell, especially the subjective perception of odors that do not exist.

Partial colectomy - the removal of part of the large intestine.

Partial mastectomy - surgery to remove a portion of the breast.

Passive accessory intervertebral movements (paivms) - investigation of accessory gliding movements occurring in a joint.

Passive physiological intervertebral movements (ppivms) - investigation of passive physiological movements, passively, to confirm restrictions seen on active movement testing.

Patellar tendonitis - inflammatory condition of the patellar ligament, usually due to overuse.

Pathologist - physician who identifies diseases by studying cells and tissues under a microscope.

Pathology - the study of diseases.

Peak flow meter - a portable, inexpensive, hand-held device used to measure how air flows from lungs in one "fast blast" to measure the ability to push air out of the lungs.

Peak torque - measure of isokinetic performance.

Pediatric dentist - a specialist in the field of dentristy - dealing particularly with the oral health care of children, from infancy through the teenage years.

Pelvic exam - a physician examination of the uterus, vagina, ovaries, fallopian tubes, bladder, and rectum.

Pelvic lymph node dissection - removal of some lymph nodes from the pelvis.

Pepsin - enzyme made in the stomach that breaks down proteins.

Peptic - related to the stomach and the duodenum, where pepsin is present.

Peptic ulcer - sore in the lining of the esophagus, stomach, or duodenum, usually caused by the bacterium helicobacter pylori. An ulcer in the stomach is a gastric ulcer; an ulcer in the duodenum is a duodenal ulcer.

Perception - process of knowing or being aware of information through the ear.

Perfusion - flow.

Perianal - area around the anus.

Pericardium - the membrane that surrounds the heart.

Perilymph fistula - leakage of inner ear fluid to the middle ear that occurs without apparent cause or is associated with head trauma, physical exertion, or barotrauma.

Perineal - related to the perineum.

Perineum - area between the anus and the sex organs.

Periodontal diseases (also called gum diseases.) - serious bacterial infections that destroy the gums and the surrounding tissues of the mouth.

Periodontist - a specialist in the field of dentristy responsible for the care and prevention of gum-related diseases, guided bone regeneration, and dental implants.

Periostitis (also called shin splints.) - inflammatory condition of the covering of the bones.

Peripheral stem cell transplantation - a process in which the stem cells (immature cells from which blood cells develop) are removed, treated with anticancer drugs, and frozen until they are returned to the patient.

Peritoneal adhesions - the peritoneum is a two-layered membrane that lines the wall of the abdominal cavity and covers abdominal organs. Sometimes organs begin to adhere to the peritoneum, requiring surgery to free the organs again.

Peritoneum - lining of the abdominal cavity.

Pessary - rubber or plastic device that is inserted through the vagina to help hold the uterus in place in women who have prolapse of the uterus.

Phalen's test - test for carpal tunnel syndrome in which the wrists are flexed for one minute.

Pharynx - space behind the mouth that serves as a passage for food from the mouth to the esophagus and for air from the nose and mouth to the larynx.

Phonology - study of speech sounds.

Photophobia - sensitivity to light.

Photorefractive keratectomy (prk) - surgical procedure using an excimer laser to change the shape of the cornea.

Physiatrist - the physician who specializes in physical medicine and rehabilitation.

Pituitary gland - gland at the base of the brain that secretes hormones and regulates and controls other hormone-secreting glands and many body processes, including reproduction.

Placenta - organ that develops in the uterus during pregnancy; links the blood supplies of a pregnant woman to the fetus to provide nutrients and remove waste products.

Placental abruption - premature detachment of the placenta from the wall of the uterus causing severe bleeding that is life threatening to both a pregnant woman and fetus.

Plantar warts - warts that occur on the sole of the foot and look like calluses; often a result of an infection or a specific virus.

Plaque, dental - film of mucus that traps bacteria on the surface of the teeth.

Plasma - the watery, straw-colored fluid which carries the cellular elements of the blood through circulation.

Platelets - cells found in the blood.

Pneumonectomy - removal of an entire lung, for cancer, lung abscesses, bronchiectasis, or extensive tuberculosis.

Polyp - a growth that projects from the lining of mucous membrane, such as the intestine.

Polyposis - presence of many polyps.

Polyunsaturated fat - a type of fat found in vegetable oils and margarines that does not appear to raise blood cholesterol levels.

Pontic tooth - false tooth.

Porcelain veneers - a ceramic material that is bonded to the front of teeth to change the tooth's color, size, and/or shape.

Portal hypertension - abnormally high blood pressure in the portal vein, which supplies the liver with blood from the intestine.

Portal vein - large vein that carries blood from the intestines and spleen to the liver.

Portosystemic shunt - operation to create an opening between the portal vein and other veins around the liver.

Positron emission tomography (pet) - a nuclear scanning procedure that gives a three-dimensional picture of the heart to provide information about the flow of blood through the coronary arteries to the heart muscle.

Post-anesthesia care unit (also called recovery room.) - the area a patient is brought to after surgery to recover.

Postcholecystectomy syndrome (also called biliary dyskinesia.) - condition that occurs after a gallbladder removal in which the muscle between the gallbladder and the small intestine does not work properly, causing pain, nausea, and indigestion.

Posterior chamber of the eye - the back section of the eye's interior.

Posterior optical segment - portion of the eye located behind the crystalline lens; includes the vitreous, choroid retina, and optic nerve.

Posterior vitreous detachment (pvd) - the separation of the vitreous from the retina.

Postgastrectomy syndrome - condition that occurs after an operation to remove the stomach (gastrectomy). (see also dumping syndrome.)

Postlingually deafened - individual who becomes deaf after having learned language.

Postvagotomy stasis - delayed stomach emptying; often occurs after surgery on the vagus nerve.

Predisposition - tendency to develop a certain disease.

Prednisolone - one type of corticosteroid medication, usually used for inflammation.

Prelingually deafened - individual who is either born deaf or who has lost hearing early in childhood, before learning language.

Presbycusis - loss of hearing that gradually occurs because of changes in the inner or middle ear in individuals as they grow older.

Preterm labor - labor that begins before the 37th week of pregnancy.

Prevalence - statistic that equals the total number of people in a population with a certain disease at a given time.

Prick skin test - a test to determine if a person is allergic to certain substances. A physician places a drop of the substance being tested on the persons forearm or back and pricks the skin with a needle, allowing a tiny amount to enter the skin. If the person is allergi

Primary sclerosing cholangitis - inflammation, scarring, and narrowing of the bile ducts inside and outside the liver.

Proctalgia fugax - intense pain in the rectum that occasionally happens at night; caused by muscle spasms around the anus.

Proctectomy - operation to remove the rectum.

Proctocolectomy (also called coloproctectomy.) - operation to remove the colon and rectum.

Proctocolitis - inflammation of the colon and rectum.

Proctologist - physician who specializes in disorders of the anus and rectum.

Proctoscope - short, rigid metal tube used to look into the rectum and anus.

Proctoscopy - looking into the rectum and anus with a proctoscope.

Proctosigmoiditis - inflammation of the rectum and the sigmoid colon.

Proctosigmoidoscopy - endoscopic examination of the rectum and sigmoid colon. (see also endoscopy.)

Progestin - synthetic form of the female sex hormone progesterone.

Prognosis - a prediction of the course of the disease.

Prolapse - condition that occurs when a body part slips from its normal position.

Prolapse of the uterus - displacement of the uterus down into the vagina; caused by a weakening of supporting tissues in the pelvis.

Proprioceptive neuromuscular facilitation (pnf) - techniques used to improve motor skills through positive motor transfer, using the principles of facilitation/inhibition; irradiation/reinforcement; reciprocal innervation.

Prostatalgia - pain in the prostate gland.

Prostate acid phosphatase (pap) - an enzyme produced by the prostate that is elevated in some patients when prostate cancer has spread beyond the prostate.

Prostatectomy - surgical procedure for the partial or complete removal of the prostate.

Prostate-specific antigen (psa) - an antigen made by the prostate gland and found in the blood; may indicate cancer in the prostate gland.

Prostate-specific antigen (psa) blood test - a blood test used to help detect prostate cancer by measuring a substance called prostate-specific antigen produced by the prostate.

Prostatism - any condition of the prostate that causes interference with the flow of urine from the bladder.

Prostatitis - an inflamed condition of the prostate gland that may be accompanied by discomfort, pain, frequent urination, infrequent urination, and, sometimes, fever.

Prosthodontist - a dental specialist who has undergone additional training and certification in the restoration and replacement of broken teeth with crowns, bridges, or removable prosthetics (dentures).

Proton pump inhibitors - medications that stop the stomach's acid pump.

Pruritus ani - itching around the anus.

Pubic symphysis - anterior joint of the pelvis.

Pudendal block - pain-relieving procedure used during childbirth in which an anesthetic is injected into tissues surrounding the pudendal nerves on either side of the vagina; blocks pain in the tissues between the vagina and anus.

Pulmonary - pertains to lungs and respiratory system.

Pulmonary artery - blood vessel delivering oxygen-poor blood from the right ventricle to the lungs.

Pulmonary hypertension - abnormally high blood pressure in the arteries of the lungs.

Pulmonary vein - the vessel that carries newly oxygenated blood to the heart from the lungs.

Pupil - the dark center in the middle of the iris through which light passes to the back of the eye.

Pupillary response - the constriction or dilation of the pupil as stimulated by light.

Pyloric sphincter - muscle between the stomach and the small intestine.

Pylorus - opening from the stomach into the top of the small intestine (duodenum).

Pyramidal pathway - a collection of nerve tracts that travel from the cerebral cortex through the pyramid of the medulla oblongata in the brainstem to the spinal cord. Within the pyramid of the medulla, fibers cross from one side of the brain to the opposite side of the spin.