The posterior cranial fossa is 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 minus the mandible is called the ''cranium''. The cavity is formed by eight cranial bones known as the neurocranium that in ...

, located between the

foramen magnum The foramen magnum ( la, great hole) 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 oblon ...

and

tentorium cerebelli The cerebellar tentorium or tentorium cerebelli (Latin for "tent of the cerebellum") is an extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes. Structure The cerebellar tentorium is an arche ...

. It contains 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 cont ...

and

cerebellum The cerebellum (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 or even larger. In humans, the cerebel ...

. This is the most inferior of the fossae. It houses the cerebellum, medulla and pons. Anteriorly it extends to the apex of the petrous temporal. Posteriorly it is enclosed by the occipital bone. Laterally portions of the squamous temporal and mastoid part of the temporal bone form its walls.

Features

Foramen magnum

The most conspicuous, large opening in the floor of the fossa. It transmits the medulla, the ascending portions of the spinal accessory nerve (XI), and the vertebral arteries.

Internal acoustic meatus

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

vestibulocochlear The vestibulocochlear nerve or auditory vestibular nerve, also known as the eighth cranial nerve, cranial nerve VIII, or simply CN VIII, is a cranial nerve that transmits sound and equilibrium (balance) information from the inner ear to the b ...

(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 The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three a ...

Jugular foramen

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

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 overlies the occipital lobe ...

and transmits the

internal jugular vein The internal jugular vein is a paired jugular vein that collects blood from the brain and the superficial parts of the face and neck. This vein runs in the carotid sheath with the common carotid artery and vagus nerve. It begins in the posteri ...

(actually begins here), the

glossopharyngeal The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...

(IX), the

vagus The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right v ...

(X) and the accessory (XI) nerves.

Anterior condylar (hypoglossal) canal

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

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 A jugular foramen is one of the two (left and right) large foramina (openings) in the base of the skull, located behind the carotid canal. It is formed by the temporal bone and the occipital bone. It allows many structures to pass, including the ...

, where the

sigmoid sinus The sigmoid sinuses (sigma- or s-shaped hollow curve), also known as the , are venous sinuses within the skull that receive blood from posterior dural venous sinus veins. Structure The sigmoid sinus is a dural venous sinus situated within the du ...

becomes the

. 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 The endocranium in comparative anatomy is a part of the skull base in vertebrates and it represents the basal, inner part of the cranium. The term is also applied to the outer layer of the dura mater in human anatomy. Structure Structurally, t ...

, and holds the most basal parts of the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

Related pathophysiology

An underdeveloped posterior cranial fossa can cause

Arnold–Chiari malformation Chiari malformation (CM) is a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum (the opening at the base of the skull). CMs can cause headaches, difficu ...

. 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 The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria. Structure Structures found at the base of the skull are for ...

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.

External links

* {{Authority control Skull