Fossae

Fossa is a term in anatomy describing a shallow depression or hollow on a bone or other surface. Fossae serve as articular surfaces for joints, as spaces that accommodate soft tissues such as muscles, nerves, or vessels, and as recesses that guide or house structures. The word is used to name many specific depressions throughout the skeleton, and the plural form is fossae.

In the skull base, there are the cranial fossae—anterior, middle, and posterior—defined by the surrounding bones. Each fossa forms a region that supports particular brain structures and provides pathways for nerves and vessels. The frontal, temporal, and occipital bones contribute to these basinner regions, and various foramina lie at their margins.

Common named fossae include the lacrimal fossa, which houses the lacrimal sac; the mandibular (glenoid) fossa of the temporal bone, which forms part of the temporomandibular joint; and the iliac fossa, a large interior depression on the inner surface of the ilium. Other well-known fossae are the olecranon fossa, coronoid fossa, and radial fossa on the distal humerus, all related to elbow articulation. The glenoid (glenoid cavity) of the scapula forms the socket for the humeral head in the shoulder joint.

In skull-base anatomy, deep spaces such as the pterygopalatine fossa and infratemporal fossa are named for their locations and contents, including nerves and arteries that traverse the region.

Etymology traces to the Latin fossa, meaning ditch or trench. Understanding fossae involves recognizing their roles as articulation surfaces, attachment sites, or passageways for neurovascular structures.