The basilar part of the occipital bone (also basioccipital) 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.
The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly, bat or wasp with its wings extended. The name presumably originates from this shape, since sphekodes (σφηκώδης) means 'wasp-like' in Ancient Greek.
The occipital bone (/ˌɒkˈsɪpɪtəl/) is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lobes of the cerebrum. At the base of the skull in the occipital bone, there is a large oval opening called the foramen magnum, which allows the passage of the spinal cord.
Like the other cranial bones, it is classed as a flat bone. Due to its many attachments and features, the occipital bone is described in terms of separate parts. From its front to the back is the basilar part, also called the basioccipital, at the sides of the foramen magnum are the lateral parts, also called the exoccipitals, and the back is named as the squamous part. The basilar part is a thick, somewhat quadrilateral piece in front of the foramen magnum and directed towards the pharynx. The squamous part is the curved, expanded plate behind the foramen magnum and is the largest part of the occipital bone.
The tectorial membrane of atlanto-axial joint (occipitoaxial ligaments) is a tough membrane/broad, strong band representing the superior-ward prolongation of the posterior longitudinal ligament (the two being continuous).
It attaches inferiorly onto (the posterior aspect of) the body of axis. It broadens superiorly. Superiorly, the membrane extends deep to the median atlanto-axial joint and its associated ligaments, then through the foramen magnum into the cranial cavity where it ends by attaching onto the basilar part of occipital bone superior to the foramen magnum.