Sphenoid Bone

The sphenoid bone is a large butterfly-shaped bone of the skull. Together with the lower part of the occipital bone, it constitutes the biggest part of the base of the human cranium. It is much wider than it is long as its lateral sides stretches out from the center to form the greater wings (right and left) and the lesser wings of bone.

Anteriorly and superiorly, the sphenoid is bounded by the lower border of the frontal bone. Laterally, it is bounded by the temporal, and posteriorly by both the temporal and occipital bone, with which it forms the foramen magnum, which is a large opening for the passage of the spinal cord into the skull. The inferior surface of the orbitofrontal lobe of the brain rests on the lowest part of the greater wing.

Right at the center of the sphenoid, there is a small bone structure called the sella turcica, which is formed by a deep depression known as the hypophyseal fossa; the pituitary gland sits in the sella turcica. The size of the hypophyseal fossa depends on the size of the pituitary. In the greater wing, there are two small openings; one of them is the foramen ovale, which is a passage for nerves and blood vessels; the other the foramen rotundum, which is an small aperture for the maxillary branch of the trigeminal nerve (CN V).

Below, drawing of sphenoid and occipital bone (superior aspect), with names of different parts