n. 1. an air cavity within a bone, especially any of the cavities within the bones of the face or skull (see paranasal sinuses). 2. any wide channel containing blood, usually venous blood. Venous sinuses occur, for example, in the dura mater and drain blood from the brain. 3. a pocket or bulge in a tubular organ, especially a blood vessel; for example, the carotid sinus. 4. (sinus tract) an infected blind-ending epithelium-lined tract leading from a focus of infection to the surface of the skin or a hollow organ. See pilonidal sinus.
1. an air cavity within a bone, especially any of the cavities within the bones of the face or skull (see paranasal sinuses). 2. any wide channel containing blood, usually venous blood. Venous sinuses occur, for example, in the dura mater and drain blood from the brain. 3. a pocket or bulge in a tubular organ, especially a blood vessel; for example, the carotid sinus. 4. (sinus tract) an infected blind-ending epithelium-lined tract leading from a focus of infection to the surface of the skin or a hollow organ. See pilonidal sinus.
