Basilar part of occipital bone

The basilar part of the occipital bone extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline.

In the young skull this area is rough and uneven, and is joined to the body of the sphenoid by a plate of cartilage.

By the twenty-fifth year this cartilaginous plate is ossified, and the occipital and sphenoid form a continuous bone.

Surfaces
On its lower surface, about 1 cm. in front of the foramen magnum, is the pharyngeal tubercle which gives attachment to the fibrous raphé of the pharynx.

On either side of the middle line the Longus capitis and Rectus capitis anterior are inserted, and immediately in front of the foramen magnum the anterior atlantoöccipital membrane is attached.

The upper surface presents a broad, shallow groove which inclines upward and forward from the foramen magnum; it supports the medulla oblongata, and near the margin of the foramen magnum gives attachment to the membrana tectoria.

On the lateral margins of this surface are faint grooves for the inferior petrosal sinuses.