Middle cranial fossa

The middle cranial fossa is supported by the basisphenoid bone, extending from the wings of the presphenoid bone to the sphenooccipital crest and the crest of the petrous part of the temporal bone.

Its medial region is occupied by the sella turcica, at the center of which lies the hypophysial fossa. The hypophysial fossa is bordered caudally by the dorsum sellae and rostrally by the overhanging surface of the presphenoid bone, which separates it from the chiasmatic groove.

Each of these two ridges bears a pair of clinoid processes, one rostral and the other caudal.

On either side of the median region are two adjacent longitudinal grooves:

• the groove of the ophthalmic nerve, located medially, which houses the ophthalmic nerve, the motor nerves of the eye, and important vascular structures;

• the groove of the maxillary nerve, located laterally, which houses the maxillary nerve.

Variation:

In carnivores, the clinoid processes are well-defined.

In equids, the clinoid processes are poorly developed.

In ruminants, the clinoid processes are also poorly developed, and the grooves of the ophthalmic and maxillary nerves are fused, forming a single opening, the orbitorotundum foramen.

In pigs, these two sulci also fuse, forming the orbitorotundum foramen.