The basilar part of the

occipital bone The occipital bone () is a neurocranium, 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 lob ...

(also basioccipital) extends forward and upward from the

foramen magnum The foramen magnum () is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblongata, passes thro ...

, 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 raphe of the pharynx. On either side of the middle line the

longus capitis The longus capitis muscle (Latin for ''long muscle of the head'', alternatively rectus capitis anticus major) is broad and thick above, narrow below, and arises by four tendinous slips, from the anterior tubercles of the transverse processes of th ...

and rectus capitis anterior are inserted, and immediately in front of the

the

anterior atlantooccipital membrane The anterior atlantooccipital membrane (anterior atlantooccipital ligament) is a broad, dense membrane extending between the anterior margin of the foramen magnum (superiorly), and (the superior margin of) the anterior arch of atlas (inferiorly). ...

is attached. The ''upper surface'', which constitutes the lower half of the clivus, presents a broad, shallow groove which inclines upward and forward from the foramen magnum; it supports the

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...

, and near the margin of the foramen magnum gives attachment to the

tectorial membrane The tectoria membrane (TM) is one of two acellular membranes in the cochlea of the inner ear, the other being the basilar membrane (BM). "Tectorial" in anatomy means forming a cover. The TM is located above the spiral limbus and the spiral org ...

On the lateral margins of this surface are faint grooves for the

inferior petrosal sinus The inferior petrosal sinuses are two small sinuses situated on the inferior border of the petrous part of the temporal bone, one on each side. Each inferior petrosal sinus drains the cavernous sinus into the internal jugular vein. Structure Th ...

es.

Additional images

File:Basilar part of occipital bone - animation02.gif,

Occipital bone The occipital bone () is a neurocranium, 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 lob ...

. Basilar part shown in red. File:Basilar part of occipital bone - animation04.gif,

Human skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominen ...

seen from below. Basilar part shown in red. File:Basilar part of occipital bone - animation06.gif, Human skull seen from above (

parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

s have been removed). Basilar part shown in red. File:Parsbasilaris(adult).PNG, Occipital bone. Outer surface. File:Gray307.png, Membrana tectoria, transverse, and alar ligaments. File:Gray387.png, The anterior vertebral muscles. File:Slide26hhhh.JPG, Basilar part of occipital bone File:Slide13jjjj.JPG, Basilar part of occipital bone File:Slide7pppp.JPG, Basilar part of occipital bone File:Occipital bone dissection.jpg, Tympanic cavity. Facial canal. Internal carotid artery.

References

External links

* Bones of the head and neck {{musculoskeletal-stub