stoma

Botany One of the minute pores in the epidermis of a leaf or stem through which gases and water vapor pass. Also called stomate.

Anatomy A small aperture in the surface of a membrane.

A surgically constructed opening, especially one in the abdominal wall that permits the passage of waste after a colostomy or ileostomy.

Zoology A mouthlike opening, such as the oral cavity of a nematode.

Botany One of the tiny openings in the epidermis of a plant, through which gases and water vapor pass. Stomata permit the absorption of carbon dioxide necessary for photosynthesis from the air, as well as the removal of excess oxygen. Stomata occur on all living plant parts that have contact with the air; they are especially abundant on leaves. A single leaf may have many thousands of stomata. Each stoma is generally between 10 to 30 microns in length and is surrounded by a pair of crescent-shaped cells, called guard cells. The guard cells can change shape and close the stoma in order to prevent the loss of water vapor. See Note at transpiration.

Zoology A mouthlike opening, such as the oral cavity of a nematode.

Medicine A temporary or permanent opening in a body surface, especially the abdomen or throat, that is created by a surgical procedure, such as a colostomy or tracheostomy.