A large vein formed by the union of the splenic and superior mesenteric veins. The portal vein conveys venous blood to the liver for detoxification before the blood is returned to circulation via the hepatic veins.
- 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.
- Positive clinical trial
Inconclusive clinical trial; Negative clinical trial; Non-inferior clinical trial.
- Positive pressure ventilation
The provision of air 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, in the event of inadequate spontaneous ventilation or respiratory paralysis. The mechanical ventilator was invented in […]
- Positive, false
A result that indicates that a given condition is present when it is not. An example of a false positive would be if a particular test designed to detect cancer returns a positive result but the person does not have ‘cancer.
- Positron emission tomography
Unlike CT or MRI, which look at anatomy or body form, PET studies metabolic activity or body function. As a result, PET can detect tumors in lymph nodes, for example, even before they enlarge and are detectable with MRI or CT. In PET imaging, the patient receives a small intravenous injection of a radio-active medication […]