The posterior cranial fossa is the part of the

cranial cavity The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull is also known as the cranium. The cranial cavity is formed by eight cranial bones known as the neurocranium that in human ...

located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and

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 ...

. It lodges the

cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...

, and parts of the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

Anatomy

The posterior cranial fossa is formed by the sphenoid bones, temporal bones, and

. It is the most inferior of the fossae. It houses the

, medulla oblongata, and pons.

Boundaries

Anteriorly, the posterior cranial fossa is bounded by the dorsum sellae, posterior aspect of the body of sphenoid bone, and the basilar part of occipital bone/ clivus. Laterally, it is bounded by the petrous parts and mastoid parts of the temporal bones, and the lateral parts of occipital bone. Posteriorly, it is bounded by the squamous part of occipital bone.

Features

Foramen magnum

The foramen magnum is a large opening of the floor of the posterior cranial fossa, its most conspicuous feature.

Internal acoustic meatus

Lies in the anterior wall of the posterior cranial fossa. It transmits the facial (VII) and vestibulocochlear (VIII)

cranial nerves Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

into a canal in the petrous temporal bone.

Jugular foramen

Lies between the inferior edge of the petrous temporal bone and the adjacent

and transmits the internal jugular vein (actually begins here), the glossopharyngeal nerve (CN IX), vagus nerve (CN X), and accessory nerve (CN XI).

Hypoglossal canal

Lies at the anterolateral margins of the foramen magnum and transmits the hypoglossal nerve (CN XII).

Other

Also visible in the posterior cranial fossa are depressions caused by the venous sinuses returning blood from the brain to the venous circulation: Right and left transverse sinuses which meet at the confluence of sinuses (marked by the internal occipital protuberance). The transverse sinuses pass horizontally from the most posterior point of the occiput. Where the apex of the petrous temporal meets the squamous temporal, the transverse sinuses lead into sigmoid (S-shaped) sinuses (one on each side). These pass along the articulation between the posterior edge of the petrous temporal bone and the anterior edge of the occipital bones to the jugular foramen, where the sigmoid sinus becomes the internal jugular vein. Note that a superior petrosal sinus enters the junction of the transverse and sigmoid sinuses. Also an inferior petrosal sinus enters the sigmoid sinus near the jugular foramen. The posterior cranial fossa is formed in the endocranium, and holds the most basal parts of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

Clinical significance

An underdeveloped posterior cranial fossa can cause Arnold–Chiari malformation. These can be either acquired or congenital disorders.

Additional images

File:Posterior cranial fossa - animation.gif, Animation File:Cranial endobasis of a 19-20 weeks foetus 2.JPG, Posterior cranial fossa at human fetus File:Schädelbasis1.jpg, Base of skull File:Base of skull 24.jpg, Posterior cranial fossa File:Base of skull 25.jpg, Posterior cranial fossa File:Postermass.png, A tumor of the posterior fossa leading to mass effect and shift of the fourth ventricle File:Cerebellar fossa by Sanjoy Sanyal.webm, Video (44 sec). Demonstrationg how

sits in the posterior cranial fossa.

References

External links

* {{Authority control Skull Otorhinolaryngology