Internal carotid artery crosses -
Ans. C. Cavernous sinusThe internal carotid artery arises from the bifurcation of the common carotid artery, ascends in the neck and enters the carotid canal of the temporal bone. Its subsequent course is said to have petrous, cavernous and intracranial parts.Petrous parta. The petrous part of the internal carotid artery ascends in the carotid canal, curves anteromedially and then superomedially above the cartilage that fills the foramen lacerum, and enters the cranial cavity.b. It lies at first anterior to the cochlea and tympanic cavity, and is separated from the latter and the pharyngotympanic tube by a thin, bony lamella that is cribriform in the young and partly absorbed in old age. Further anteriorly, it is separated from the trigeminal ganglion by the thin roof of the carotid canal, although this is often deficient. The artery is surrounded by a venous plexus and by the carotid autonomic plexus, derived from the internal carotid branch of the superior cervical ganglion.c. The petrous part of the artery gives rise to two branches. The caroticotympanic artery is a small, occasionally double, vessel which enters the tympanic cavity by a foramen in the carotid canal and anastomoses with the anterior tympanic branch of the maxillary artery and the stylomastoid artery.d. The pterygoid artery is inconsistent: when present, it enters the pterygoid canal with the nerve of the same name, and anastomoses with a (recurrent) branch of the greater palatine artery.Cavernous parta. The cavernous part of the internal carotid artery ascends to the posterior clinoid process. It turns anteriorly to the side of the sphenoid within the cavernous sinus and then curves up medial to the anterior clinoid process, to emerge through the dural roof of the sinus. The oculomotor, trochlear, ophthalmic and abducens nerves are lateral to it within the cavernous sinus.b. This part of the artery gives off a number of small vessels. Cavernous branches supply the trigeminal ganglion, the walls of the cavernous and inferior petrosal sinuses and the nerves contained therein. A minute meningeal branch passes over the lesser wing of the sphenoid to supply the dura mater and bone in the anterior cranial fossa and also anastomoses with a meningeal branch of the posterior ethmoidal artery. Numerous small hypophysial branches supply the neurohypophysis, and are of particular importance because they form the pituitary portal system.Intracranial parta. After piercing the dura mater, the internal carotid artery turns back below the optic nerve to run between it and the oculomotor nerve. It reaches the anterior perforated substance at the medial end of the lateral fissure and terminates by dividing into the anterior and middle cerebral arteries.b. Several preterminal vessels leave the cerebral portion of the internal carotid. The ophthalmic artery arises from the anterior part of the internal carotid as it leaves the cavernous sinus, often at the point of piercing the dura, and enters the orbit through the optic canal.c. The posterior communicating artery runs back from the internal carotid above the oculomotor nerve, and anastomoses with the posterior cerebral artery (a terminal branch of the basilar artery), thereby contributing to the circulus arteriosus around the interpeduncular fossa.d. The posterior communicating artery is usually very small. However, sometimes it is so large that the posterior cerebral artery is supplied via the posterior communicating artery rather than from the basilar artery ('fetal posterior communicating artery'); it is often larger on one side only. Small branches from its posterior half pierce the posterior perforated substance together with branches from the posterior cerebral artery.e. Collectively they supply the medial thalamic surface and the walls of the third ventricle. The anterior choroidal artery leaves the internal carotid near its posterior communicating branch and passes back above the medial part of the uncus.f. It crosses the optic tract to reach and supply the crus cerebri of the midbrain, then turns laterally, recrosses the optic tract, and gains the lateral side of the lateral geniculate body, which it supplies with several branches. It finally enters the inferior horn of the lateral ventricle via the choroidal fissure and ends in the choroid plexus.g. This small, but important, vessel also contributes to the blood supply of the globus pallidus, caudate nucleus, amygdala, hypothalamus, tuber cinereum, red nucleus, substantia nigra, posterior limb of the internal capsule, optic radiation, optic tract, hippocampus and the fimbria of the fornix.
Sigmoid sinus
Straight sinus
Cavernous sinus
Sagittal sinus
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