The foramen ovale and sphenoidal angle in man

The structure of the greater wing of the sphenoid in the region of the foramen ovale and sphenoidal angle is described in both the adult human and in two partly ossified human embryos. It is shown that the foramen ovale of man is enclosed by membrane bone, derived from a medial process associated with the scaphoid fossa, and a lateral tongue, the most dorsal part of which is present in many adults as a process on the lateral margin of the foramen. These structures are parts of an extensive membrane bone which forms the larger part of the greater wing of the sphenoid. It is shown that the foramen of Vesalius represents the site of fusion between this membrane bone and the more medial, cartilaginous, ala temporalis. Various inconstant patterns of grooves and foramina in the vicinity of the foramen ovale can be interpreted as arising from the interplay of the various parts of the membrane bone and the emissary venous plexus from the middle meningeal veins to the pterygoid plexus. The embryonic anlagen of the pterygo-sphenoidal and pterygo-spinous ligaments are described, and the association of these structures with the parts of the membrane bone are discussed.