Medical Dictionary: P

painkillers: A nonmedical term for drugs that relieve pain.

palpable: Able to be felt.

pancreas: An elongated gland located against the back wall of the abdomen; it produces digestive enzymes and manufactures hormones, including insulin and glucagon, that are central to the metabolism of sugar, fat, and protein.

parasomnias: Episodic disruptive behaviors occurring during sleep, indicating abnormal or partial arousal.

parasympathetic nervous system: One of two offshoots of the autonomic nervous system; it calms body systems excited by the release of stress hormones.

parathyroid glands: Glands responsible for controlling calcium and influencing bone metabolism. There are usually four of them, located behind the thyroid.

parathyroid hormone (PTH): A hormone that regulates calcium levels. It prevents the level of blood calcium from going too low by stimulating the breakdown of bone. In addition to triggering bone loss, it can stimulate bone formation. Given appropriately, it can increase bone mass, and is used as a treatment for osteoporosis.

paroxysmal hemicrania: A disorder resembling cluster headache, but with shorter and more frequent attacks.

passive immunity: Immunity that is conferred by another, such as a mother’s antibodies protecting her baby during gestation and after birth (via the substance known as colostrum in the milk ducts).

patch test: A skin test used to diagnose contact dermatitis.

patella: The bone that forms the kneecap.

pathogen: A disease-causing microbe.

pathology: The underlying abnormalities in biology and physiology that contribute to or are characteristic of a disease.

patient-controlled analgesia (PCA): A method that allows a patient to control — within limits — the amount and timing of pain medication received.

peak bone mass: The greatest amount of bone tissue that a person has during his or her life; typically reached by age 30.

peak flow meter: A device to assess lung function, commonly used to diagnose and monitor asthma.

peak flow meter: A simple handheld device used to measure peak flow.

peak flow: A measure of how fast you can blow air out of your lungs. In asthma, your peak flow reflects the extent to which your bronchial tubes are normally open or abnormally narrowed.

pelvic floor: The supportive network of muscles that extends from the pubic bone to the tailbone with openings for the urethra and anus as well as the vagina in women.

penile prosthesis: A rigid or inflatable device that is surgically implanted in the penis to make it erect.

pepsin: A name for several enzymes secreted by the stomach to break down protein.

peptic ulcer: A raw, crater-like break in the mucosal lining of the stomach or duodenum.

percutaneous diskectomy: The removal of part of an intervertebral disk by means of a narrow probe inserted through the skin and muscle of the back.

percutaneous electrical nerve stimulation (PENS): A variation of TENS in which needles are used to deliver low-voltage electrical current under the skin. Like TENS, this therapy prevents pain signals traveling through small nerve fibers from reaching the brain.

perimenopause: The phase starting when periods become irregular and lasting until a year after the last period.

perineum: The area of skin between the vagina and anus in women, and between the scrotum and anus in men.

perineum: The skin and tissue between the scrotum and the anus.

periodic limb movement disorder (PLMD): Syndrome characterized by periodic jerking of the legs during sleep.

peripheral neuropathy: Damage to the long nerves radiating from the spine to the arms and legs.

peripheral vascular disease: A disorder caused by the blockage of blood vessels to the brain and extremities.

peripheral vision: Side vision, or what the eye perceives outside the direct line of vision.

peristalsis: Wavelike movement of intestinal muscles that propels food along the digestive tract.

peritoneal dialysis: Treatment for kidney failure that allows patients to cleanse their blood inside the body, using one of several devices.

peritonitis: Inflammation of the membrane lining the abdominal cavity.

personal emergency response system: A device worn around the neck or wrist that allows you to summon help by pressing a button.

pessary: A device worn in the vagina to support or correct the position of the uterus, rectum, or bladder.

Peyronie’s disease: A disorder in which some of the tissue inside the penis becomes scarred, causing the penis to bend at an angle during an erection.

phagocytes: Cells that can ingest other cells, bacteria, and foreign particles.

photorejuvenation: The use of intense pulsed light to improve skin tone and texture.

physiatrist: A physician who specializes in physical medicine and rehabilitation.

phytochemicals: Substances made by plants that affect their taste, color, scent, and other properties. They also have biological effects in the human body. Some are phytoestrogens, chemicals that behave like (or sometimes block the action of) the hormone estrogen. Lycopene, found in tomatoes, is one phytochemical thought to have beneficial effects for people.

phytoestrogen: A plant component that mimics the effects of estrogen hormones in the body.

pituitary gland: A pea-sized endocrine gland tucked into a bony space beneath the brain. It controls and regulates the thyroid and other glands throughout the endocrine system and receives input and influence from the hypothalamus. It produces adrenocorticotropic hormone (ACTH), which controls the secretion of cortisol by the adrenal glands. This helps trigger the “fight-or-flight” response.

placebo: A therapy that physically resembles an agent being tested in a study, but which itself has no active ingredient. Placebos are used in clinical trials to compare the effects of receiving an in­active pill to a pill containing an active ingredient.

plantar fascia: The ligament-like structure that connects the heel to the ball of the foot.

plantar fasciitis: An inflammation of the plantar fascia; the leading cause of heel pain.

plantar wart: A wart on the sole of the foot.

plaque: A fatty buildup of cholesterol, calcium, and other substances inside a blood vessel.

plasma cells: Antibody-secreting cells that result from the clonal expansion of B cells after they have met their specific antigens.

plasmin: An enzyme that breaks down fibrin and dissolves blood clots.

platelets: Minute, colorless disks in the blood that are instrumental in clotting.

polyps: Small, mushroom-shaped growths on the lining of the colon.

polysomnography: Simultaneous recording of brain waves and other measures of physiological functioning to assess sleep.

polyunsaturated fat: Beneficial fats that are liquid at room temperature and contain two or more double bonds between adjacent carbon atoms. It’s found in corn, soybean, and other vegetable oils. It’s also found in seeds, legumes, whole grains, and fatty fish, such as salmon and tuna. It has a healthful effect on blood lipids.

positive psychology: An emerging field recognized by the American Psychological Association that focuses on identifying and promoting factors that allow people to thrive.

positron emission tomography (PET): A nuclear medicine imaging technique that uses differences in energy metabolism in different areas of the body to produce a three-dimensional image of functional processes in the brain or other organs.

posterior chamber: The area behind the iris and in front of the lens that is filled with aqueous humor.

posterior heel bursitis: A type of bursitis that affects the back of the heel.

post-traumatic headache: A headache resulting from a head or neck injury, sometimes persisting for a year or more after the trauma.

post-traumatic stress disorder (PTSD): A prolonged reaction to trauma characterized by recurrent flashbacks, dreams, or intrusive thoughts about the traumatic event; withdrawal from people and certain situations; being easily startled; and having difficulty sleeping.

precursor: A substance that the body can convert into the active form of a vitamin. One example is beta carotene, which the body can convert into vitamin A as needed.

prediabetes: A condition in which a fasting plasma glucose test and/or an oral glucose tolerance test provide readings that are elevated, but not quite diabetic; raises the risk for diabetes.

pre-diabetes: A condition in which a fasting plasma glucose test and/or an oral glucose tolerance test provide readings that are elevated, but not quite diabetic; raises the risk of diabetes.

prehypertension: A condition that increases the risk of developing high blood pressure; defined as 120–139 mm Hg systolic pressure or 80–89 diastolic pressure.

presbycusis: Age-related hearing loss, typically occurring in people over age 40, that occurs when sensitive hair cells in the inner ear that pick up sound waves die off over time.

presbyopia: An inability to focus at close range that typically occurs in people in their 40s as the flexible lens of the eye becomes less elastic.

priapism: An erection that lasts longer than three hours. Emergency medical treatment is required to prevent permanent damage to the penis.

prick test: A commonly used skin test to confirm hypersensitivity to a broad range of allergens that elicit an IgE-mediated response.

primary osteoporosis: Bone loss that doesn’t result from an identifiable pathological process.

probiotic: An organism that is used medicinally; examples include bacteria such as L. acidophilus and yeasts such as Saccharomyces boulardii.

procedural memory: The long-term memory of skills and procedures, or “how-to” knowledge. Also called implicit memory.

processes: The several bony projections from each vertebra, some of which mesh with similar structures on the vertebrae immediately above and below.

prodrome: Symptoms that precede a migraine headache by hours or days, including changes in mood, appetite, or activity level.

progesterone: A female steroid hormone, produced by the ovaries after ovulation, that prepares the uterine lining for pregnancy.

progestin: A synthetic compound that produces effects similar to those of progesterone.

progestogen: Any hormone having the same effect as progesterone in the body; refers to both natural progesterone and synthetic progestin.

progressive muscle relaxation (PMR): A tool for inducing the relaxation response that involves isolating, tensing, and relaxing specific sets of muscles in sequence.

prolapse: A condition in which a part of the body drops from its normal position.

proprioception: Your body’s sense of where you are in relation to objects and other people. Depends on the functioning of a network of position-sensing nerves.

prostate-specific antigen (PSA): A protein produced by the prostate. Elevated PSA levels may indicate the presence of cancer, benign prostatic hyperplasia, or prostatitis. A PSA test measures the level of this protein in the blood.

prostatic carcinoma: Cancer of the prostate gland.

prostatic urethral stent: A small, springlike cylinder, typically made of titanium, designed to relieve pressure from prostatic tissue and improve urine flow. It is positioned in the narrowed area of the urethra and released to widen the channel.

prostatitis: An inflammation of the prostate gland, sometimes caused by a bacterial infection, which may result in painful or difficult urination.

protein: One of the three major nutrients (along with carbohydrates and fats). It is used by the body for building and repairing tissues. Protein is derived primarily from animal sources but can be found in some vegetables as well.

pseudogout: arthritis caused by crystals of calcium pyrophosphate dihydrate in the joints; also known as CPPD.

psoriasis: A common skin disease characterized by thickened patches of inflamed red skin; sometimes accompanied by painful joint swelling and stiffness.

psychodynamic therapy: A form of therapy that focuses on how life events, desires, and close relationships lead to conflict, symptoms such as anxiety or depression, and difficulty in managing life’s tasks.

psychogenic erectile dysfunction: Difficulty in getting or maintaining erections because of a psychological cause, such as stress or depression.

puborectalis muscle: A pelvic floor muscle that forms a sling around the rectum.

pudendal nerve: The nerve that controls the muscles of the pelvic floor; plays an important role in urinary and fecal continence.

pulse pressure: The difference between your systolic and diastolic blood pressures. May help predict heart disease risk.