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
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the hu ...
, 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 arc ...
. 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 ...
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 cerebe ...
.
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
The accessory nerve, also known as the eleventh cranial nerve, cranial nerve XI, or simply CN XI, is a cranial nerve that supplies the sternocleidomastoid and trapezius muscles. It is classified as the eleventh of twelve pairs of cranial 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 br ...
(VIII)
cranial nerves into a canal in the
petrous temporal bone.
Jugular foramen
Lies between the inferior edge of the petrous temporal bone and the adjacent
occipital bone
The occipital bone () 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 overlies the occipital lobes of the cer ...
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 poste ...
(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, just anterior (closer to the nose) to the vagus nerve. B ...
(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, 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 ...
becomes 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 poste ...
.
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, ...
, and holds the most basal parts of the
brain
A brain is an organ (biology), 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 Visual perception, vision. I ...
.
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, difficulty ...
. 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 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 cerebe ...
sits in the posterior cranial fossa.
See also
*
Anterior cranial fossa
*
Middle cranial fossa
External links
*
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Skull