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The vertebral artery runs from base to apex (prior to entering the transverse foramen of 6th cervical vertebra). [ citation needed ] The carotid tubercle separates the vertebral artery which passes directly behind it from the common carotid artery which lies directly in front of it.
The posterior cranial fossa is the part of the cranial cavity located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and occipital bone. It lodges the cerebellum, and parts of the brainstem.
The human cerebellum is located at the base of the brain, with the large mass of the cerebrum above it, and the portion of the brainstem called the pons in front of it. It is separated from the overlying cerebrum by a layer of tough dura mater called the cerebellar tentorium; all of its connections with other parts of the brain travel through the pons.
The anterior inferior cerebellar artery (AICA) is the principal vessel of the cerebellopontine angle. It also contains two cranial nerves – the vestibulocochlear nerve and the facial nerve; the cerebellar flocculus and the lateral recess of the fourth ventricle. [citation needed]
Fourth ventricle location shown in red (E), pons (B); the floor of the ventricle is to the right, the roof to the left. The fourth ventricle has a roof at its upper (posterior) surface and a floor at its lower (anterior) surface, and side walls formed by the cerebellar peduncles (nerve bundles joining the structure on the posterior side of the ventricle to the structures on the anterior side).
The lower two are called the cerebellar fossae, are quadrilateral and accommodate the hemispheres of the cerebellum. The upper fossae are separated from the lower fossae by a groove for the transverse sinuses. At the point of intersection between all four fossae is the internal occipital protuberance.
The cerebral aqueduct is roughly circular in transverse section, and measures 1-2 mm in diameter. [3] It is 15 mm long and is commonly subdivided into a pars anterior antrum, and pars posterior. [ 2 ]
The free border of the tentorium is U-shaped; it forms an aperture - the tentorial notch (tentorial incisure) - which gives passage to the midbrain.The free border of each side extends anteriorly beyond the medial end of the superior petrosal sinus (i.e. the apex of the petrous part of the temporal bone [citation needed]) to overlap the attached margin, thenceforth forming a ridge of dura ...