ankyloglossia A minor birth defect in which the flap of membrane attached to the underside of the tongue (frenulum) is too short. This shortened frenulum limits the mobility of the tongue. Ankyloglossia is also called tongue tie, from the folk belief that the anomaly causes feeding and speech problems. A child cannot feed or speak…
ankle-foot orthosis A brace, usually made of plastic, that is worn on the lower leg and foot to support the ankle, hold the foot and ankle in the correct position and correct foot drop. Abbreviated AFO. Also known as foot drop brace.
ankle joint A joint that is composed of three bones: the tibia, the fibula, and the talus. The ankle joint is responsible for the up-and-down motion of the foot. The subtalar joint is under the ankle joint, and it consists of the talus on top and calcaneus on the bottom. The subtalar joint is responsible…
ankle A complex structure made up of two joints: the true ankle joint and the subtalar joint. The ankle’s movement is constrained and controlled by ligaments, including the anterior tibiofibular ligament, which connects the tibia to the fibula; the lateral collateral ligaments, which attach the fibula to the calcaneus to give the outside of the…
anisocytosis Excessive inequality in the size of the red blood cells. Anisocytosis is apparent on a blood smear examined under a microscope.
anisocoria A condition in which the left and right pupils of the eyes are not of equal size. The size of the pupil determines how much light is let into the eye. With anisocoria, the larger pupil lets more light enter the eye. There are many causes of anisocoria, including eye injury or infection and…
anhidrosis Lack of sweating. Anhidrosis creates a dangerous inability to tolerate heat.
angle-closure glaucoma Increased pressure in the front chamber of the eye due to blockage of its normal circulation of fluid. When the iris retracts and thickens (when the pupil of the eye is wide open), it blocks the drainage pathway for fluid in the eye. This causes the pressure in the eye to soar, which…
angiotensin converting enzyme See ACE.
angiotensin A family of peptides that constrict blood vessels. Narrowing the diameter of the blood vessels causes blood pressure to rise.
angiostatin A fragment of a protein, plasminogen, that is involved in blood clotting. Angiostatin is normally secreted by tumors, and it appears to halt the process of developing new blood vessels, which is necessary to tumor development.
angiosarcoma A form of tissue cancer (sarcoma) that arises in the lining of blood vessels. Angiosarcomas tend to be aggressive, recur locally, and spread widely. Predisposing factors include lymphedema (as from a radical mastectomy), radiotherapy, foreign materials (such as steel and plastic) in the body, and environmental agents (such as arsenic solutions used to spray…