Medical Dictionary Definitions A-Z List
Medical Dictionary Definitions A - Z - «P»:
Platelet: An irregular, disc-shaped element in the
blood that assists in blood clotting. During normal blood clotting,
the platelets clump together (aggregate). Although platelets are
often classed as blood cells, they are actually fragments of large bone marrow cells called megakaryocytes....
Platelet aggregation: The clumping together of platelets in the blood. Platelet aggregation is part of the sequence of events leading to the formation of a thrombus (clot)....
Platelet count: The calculated number of platelets in a volume of blood, usually expressed as platelets per cubic millimeter (cmm) of whole blood. Platelets are the smallest cell-like structures in the blood and are important for blood clotting and plugging damaged blood vessels. Platelet counts are...
plegia: Suffix meaning paralysis or a stroke. As in cardioplegia (paralysis of the heart), hemiplegia (paralysis of one side of the body), paraplegia (paralysis of the legs), and quadriplegia (paralysis of all four extremities). From the Greek plege meaning a blow or stroke....
Pleiotropic: 1. Producing many effects.
2. Multiple effects from a single gene. For example,
the Marfan gene is pleiotropic with widespread effects and can cause long fingers and toes
(arachnodactyly), dislocation of the lens of the eye, and dissecting aneurysm of the
Pleiotropic cytokine: cytokine that affects the activity of multiple cell types. A cytokine is a small protein that has a specific effect on the interactions between cells, on communications between cells, or on the behavior of cells....
Pleomorphic: Many-formed. A tumor may be pleomorphic. Pleomorphic
is synonymous with protean (capable of assuming different shapes like the many-formed
Greek god Proteus). ...
Pleonasm: An excess in the number of parts or in the size of a growth. Pleonasm comes from a Greek word (pleonasmos) meaning exaggeration or redundancy.
A pleonasm in language is also a redundancy. It is the use of more words than those necessary to denote mere sense as, for example, in "a false li...
Plethoric: Florid, red-faced. ...
Pleura: The thin covering that protects and cushions the lungs.
The pleura is made up of two layers of tissue that are separated by a small amount of
Pleurae: Pleural of pleura (the thin covering that protects and cushions the lungs)....
Pleural: Pertaining to the pleura, the thin covering that protects the lungs. The term "pleural" is pronounced like "plural" (but does not have plural meanings)....
Pleural effusion: Excess fluid between the two membranes that envelop the lungs. These membranes are called the visceral and parietal pleurae. The visceral pleura wraps around the lung while the parietal pleura lines the inner chest wall. There is normally a small quantity (about 3 to 4 teaspoons) o...
Pleural effusion, fetal
Pleural effusion, fetal: See: Fetal pleural effusion....
Pleural space: The tiny area between the two layers
of the pleura (the thin covering that protects and cushions the lungs). The pleural space is normally filled with a small amount of fluid....