What Is the Posterior Cranial Fossa?

The posterior cranial fossa is the rearmost hollow or depressed area in the base of the cranium, which constitutes the upper part of the human skull. It is also the largest and deepest area of the skull. The posterior cranial fossa is one of the three cranial fossae, the others being the anterior cranial fossa and the middle cranial fossa. Like the other depressed areas, it bears the lobes of the brain.

Located at the base of the cranium, the posterior cranial fossa forms part of the intracranial cavity. This is the space within the skull where the brain is located, which is enclosed by membranes and uses the area's cerebrospinal fluid as a protective cushion against shock or trauma. It is also called the cranial cavity or intracranial space. The endocranium — a part of the cranium's base that denotes its bottom, inner part — is responsible for forming the posterior cranial fossa.

Behind the posterior cranial fossa are the pons and the medulla oblongata. Both are found at the lower region of the brain's posterior part known as the brain stem, with the pons placed above the medulla. At the front, the posterior cranial fossa houses the cerebellum, which is the part of the brain chiefly responsible for motor control.

The posterior cranial fossa possesses several boundaries. At the front, it is enclosed by a square-shaped plate called the dorsum sellae, a sloping depression called the clivus from the sphenoid bone, and the bottom part of the occipital bone. The rear is bounded by the flat part of the occipital bone. A small portion of the parietal bone's inferior angle seals the top and bottom part of the fossa. The sides, also referred to as its walls, consist of the pyramid-shaped and posterior part of the temporal bone as well as the lateral round prominence of the occipital bone.

Other features of the posterior cranial fossa include the foramen magnum, the tentorium cerebelli and the jugular foramen. The foramen magnum is a large opening in the occipital bone that is responsible for providing the medulla oblongata to enter and exit the skull. Also known as the cerebellar tentorium, the tentorium cerebelli is named for it function as a "tent" for the cerebellum; it sets apart that section of the brain from the inferior area of the occipital lobes. The jugular foramen is a hole at the base of the skull that transports certain cranial and accessory nerves.