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Medical Dictionary Definitions A-Z List

Medical Dictionary Definitions A - Z - «P»:

  1. Porphyria Porphyria
    Porphyria: A diverse group of diseases in which the production of heme is disrupted. Porphyria is derived from the Greek word "porphyra", which means purple. When heme production is faulty, porphyrins are overproduced and lend a reddish-purple color to urine. All forms of porphyrias are inherited. T...
  2. Porphyria cutanea tarda Porphyria cutanea tarda
    Porphyria cutanea tarda: Literally, the late skin form of porphyria, a genetic photosensitive (light-sensitive) skin disease with onset in adult life with substances called uroporphyrins in the urine due to a deficiency of uroporphyrinogen decarboxylase (UROD), an enzyme required for the synthesis o...
  3. Port wine stain Port wine stain
    Port wine stain: A mark on the skin that resembles port wine (porto) in its rich ruby red color. Due to an abnormal aggregation of capillaries, a port wine stain is a type of hemangioma. A port wine stain on the face is a sign of the Sturge-Weber syndrome....
  4. Portable generator safety Portable generator safety
    Portable generator safety: Safety, an essential matter in using a portable residential or recreational generator. Portable residential generators may be used to supply essential home power needs during power-outages, for powering cabin appliances, or for power tools needed during projects. Recreatio...
  5. Portal vein Portal vein
    Portal vein: A large vein that carries blood from the stomach and the intestines to the liver. The portal vein is formed by the union of the splenic and superior mesenteric veins. It conveys venous blood to the liver for detoxification before the blood is returned to the circulation via the h...
  6. Position, anatomical Position, anatomical
    Position, anatomical: See: Anatomical position....
  7. Positional cloning Positional cloning
    Positional cloning: Cloning a gene based simply on knowing its position in the genome without any idea of the function of that gene. Because this is the reverse of how things have been traditionally done, it has also been called reverse genetics. ...
  8. Positive clinical trial Positive clinical trial
    Positive clinical trial: A clinical trial that shows that the new treatment has a large beneficial effect and is superior to standard treatment. See: Clinical trials. See also: Inconclusive clinical trial; Negative clinical trial; Non-inferior clinical trial....
  9. Positive end-expiratory pressure Positive end-expiratory pressure
    Positive end-expiratory pressure: Better known as PEEP. See: PEEP....
  10. Positive pressure ventilation Positive pressure ventilation
    Positive pressure ventilation: The provision of oxygen under pressure by a mechanical respirator, a machine designed to improve the exchange of air between the lungs and the atmosphere. The device is basically designed for administering artificial respiration, especially for a prolonged period,...
  11. Positive, false Positive, false
    Positive, false: A result that is erroneously positive when a situation is normal. An example of a false positive: a particular test designed to detect cancer of the toenail is positive but the person does not have toenail cancer....
  12. Positive-strand RNA virus Positive-strand RNA virus
    Positive-strand RNA virus: Also known as a sense-strand RNA virus, a virus whose genetic information consists of a single strand of RNA that is the positive (or sense) strand which encodes mRNA (messenger RNA) and protein. Replication in positive-strand RNA viruses is via a negative-strand intermedi...
  13. Positron emission tomography Positron emission tomography
    Positron emission tomography: PET. A highly specialized imaging technique that uses short-lived radioactive substances to produce three-dimensional colored images of those substances functioning within the body. These images are called PET scans and the technique is termed PET scanning. PET scanning...
  14. Post Post
    Post: Short for postmortem examination (an autopsy)....
  15. Post-exposure prophylaxis Post-exposure prophylaxis
    Post-exposure prophylaxis: A treatment administered following exposure to a harmful agent which attempts to block or reduce injury or infection. Prophylaxis means a defense or protection. Post-exposure prophylaxis (PEP), for example, might concern the treatment of a health care worker exposed by a n...