The Sphenoid bone consists of a small body with several paired processes, the important ones being the great wings and the pterygoid plates. The latter, four in number, project downwards behind the nose. The great wings have at their extremities triangular surfaces, which articulate with the frontal, parietal, and temporal bones; these lock the sides of the cranium anteriorly. The body lies between the ethmoid (which articulates with the nasal parts of the frontal bone) and the basilar process of the occipital bone, so locks the cranium in the antero-posterior direction. The great wings also form part of the orbital cavity, and between the great wing and the lesser wing is the sphenoidal fissure at the back of the orbital cavity through which the first part of the fifth nerve passes. The foramen rotundum and foramen ovale are in the great wing.