Glossary
P
- Phylum
- The segmentation of the animal kingdom into about 30 major groups collectively known as phyla. The members of each phylum share the same basic structure and organization. For instance, fish, birds, and human beings belong to one phylum - the Chordata - because all have spinal cords.
- Pituitary gland
- A cherry-like organ at the base of the brain responsible for controlling growth and development.
- Placebo
- In clinical trials, an inert substance identical in appearance to the substance being tested.
- Placenta
- A highly vascular organ on the inner wall of the uterus permitting exchange of gases and substances between mother and baby.
- Plaque
- 1. A small disk-shaped formation or growth; a patch. 2. A deposit of fatty material on the inner lining of an arterial wall, characteristic of atherosclerosis.
- Plasma
- The liquid portion of the blood (after the cells have been removed).
- Platelet
- Cell fragments that are important in the formation of blood clots, in the stemming of blood loss and in the repair of injury to blood vessels.
- Pneumonia
- Infection of the actual lung tissue (in comparison to the airways).
- Population
- The total number of inhabitants constituting a particular race, class, or group in a specified area.
- Posterior
- Situated nearer the rear part of the body.
