Dictionary

parasitic Having to do with a parasite, as in a parasitic infection; or acting like a parasite by taking nourishment from another.

parasomnia A sleep disorder in which odd or dangerous events occur that intrude on sleep. The parasomnias include sleep talking, sleepwalking (somnambulism), sleep terrors, REM behavior disorder, and nocturnal dissociative disorder.

parasympathetic nervous system The part of the involuntary nervous system that serves to slow the heart rate, increase intestinal and glandular activity, and relax the sphincter muscles. The parasympathetic nervous system, together with the sympathetic nervous system, constitutes the autonomic nervous system.

parathormone A hormone that is made by the parathyroid glands and is critical to maintaining calcium and phosphorus balance. Deficiency of parathormone results in abnormally low calcium in the blood (hypocalcemia). Excessive parathormone leads to elevated calcium levels in the blood and calcium deposition in cartilage. Also known as parathyroid hormone and parathyrin.

parathyrin See parathormone.

parathyroid gland The gland that regulates calcium metabolism. The parathyroid gland is located behind the thyroid gland in the neck. It secretes a hormone called parathormone that is critical to the metabolism of calcium and phosphorus. Although the number of parathyroid glands can vary, most people have four. The parathyroid glands appear as a pair,…

parathyroid hormone See parathormone.

parathyroids, hypoplasia of the thymus and See DiGeorge syndrome.

parenchyma The key elements of an organ essential to its functioning, as distinct from the capsule that encompasses it and other supporting structures.

parenteral Not delivered via the intestinal tract. For example, parenteral nutrition is feeding that is delivered intravenously.

Pap test A screening test for cervical cancer that involves the microscopic examination of cells collected from the cervix, smeared on a slide, and specially stained. A Pap test can reveal premalignant and malignant changes in the cells, as well as changes that are due to noncancerous conditions, such as inflammation. Named after the physician…

papillary tumor A tumor that is shaped like a small mushroom, with its “stem” attached to an organ, such as the inner lining of the bladder.