Orbital surface

The orbital part (Pars orbitalis) /orbital surface (Facies orbitalis) of the frontal bone extends rostrally to the orbitotemporal crest. It is concave and forms the medial wall of the orbit that shows

1) the orbital opening of the supra-orbital foramen and canals;

2) the shallow fossa for the lacrimal sac/gland (Fossa sacci lacrimalis) against the zygomatic process;

3) more medially, the trochlear fovea (Fovea trochlearis) completed on the living by a fibrocartilaginous ring for the reflexion of the dorsal oblique muscle of the eye;

4) below and caudally, the ethmoidal foramen (Foramen ethmoidale), that gives access to the rostral part of the cerebral cavity. This orifice is double in Carnivorous; in Equidae, it is carved at the limit of the sphenoid and frontal bones and is therefore only marked by an incisure on the medial border of the frontal bone.

Finally, fully ventrally, the limit of the orbit is marked by the inferior orbital crest (Crista orbitalis inferior), well visible in Dogs, less in other species.