Internal carotid artery

The internal carotid artery (a.carotis interna) supplies blood to the brain and the organ of vision. The internal carotid artery is divided into the cervical, petrosal, cavernous and cerebral parts. This artery does not give off branches on the neck. The cervical part (pars cervicalis) is located laterally and behind, and then medially from the external carotid artery. Between the pharynx medially and the internal jugular vein laterally, the internal carotid artery rises vertically upward to the external opening of the carotid canal. Behind and medially from the internal carotid artery are the sympathetic trunk and vagus nerve, in front and laterally - the hypoglossal nerve, above - the glossopharyngeal nerve. In the carotid canal is the petrosal part (pars petrosa) of the internal carotid artery, which forms a bend and gives off thin carotid-tympanic arteries (aa.carotico-tympanicae) into the tympanic cavity.

Upon exiting the carotid canal, the internal carotid artery makes an upward bend and lies in the short groove of the same name in the sphenoid bone. The cavernous part (pars cavernosa) of the artery is located in the thickness of the cavernous sinus of the dura mater of the brain. At the level of the optic canal is the cerebral part (pars cerebralis), here the artery makes another bend, facing forward with its convexity. At this point, the ophthalmic artery branches off from the internal carotid artery. At the inner edge of the anterior clinoid process, the internal carotid artery divides into its terminal branches - the anterior and middle cerebral arteries.

The ophthalmic artery (a.ophthalmica) branches off in the area of the last bend of the internal carotid artery and, together with the optic nerve, enters the orbit through the optic canal. The ophthalmic artery then follows the medial wall of the orbit to the medial angle of the eye, where it divides into its terminal branches - the medial arteries of the eyelids and the dorsal artery of the nose.

The following branches depart from the ophthalmic artery:

1. the lacrimal artery (a.lacrimalis) runs between the superior and lateral rectus muscles of the eye, giving them branches to the lacrimal gland; the lateral arteries of the eyelids (aa.palpebrales laterales) also separate from the lacrimal artery;
2. the long and short posterior ciliary arteries (aa.ciliares posteriores longae et breves) pierce the sclera and penetrate the choroid;
3. the central retinal artery (a.centralis retinae) enters the optic nerve and reaches the retina;
4. muscular arteries (aa. musculares) go to the superior rectus and oblique muscles of the eyeball. From the muscular arteries, the anterior ciliary arteries (aa. ciliares anteriores; 5-6 in total) branch off and enter the anterior sections of the sclera of the eyeball, ending in the iris, and the anterior conjunctival and ciliary arteries (aa. conjuctivales anteriores), which go to the conjunctiva of the eye;
5. the posterior ethmoidal artery (a.ethmoidalis posterior) follows to the mucous membrane of the posterior cells of the ethmoid bone through the posterior ethmoidal opening;
6. the anterior ethmoidal artery (a.ethmoidalis anterior) passes through the anterior ethmoidal opening, where it divides into its terminal branches. One of these branches, the anterior meningeal branch (r.meningeus anterior), enters the cranial cavity and supplies the dura mater of the brain. Other branches penetrate under the ethmoid plate of the ethmoid bone and supply the mucous membrane of the ethmoid cells, as well as the anterior parts of the lateral walls and the nasal septum;
7. The supraorbital artery (a.supraorbitalis) branches off from the ophthalmic artery where it passes over the optic nerve. The supraorbital artery is adjacent to the upper wall of the orbit. Then, in the region of the supraorbital notch, it turns upward (together with the nerve of the same name), branches in the muscles and skin of the forehead;
8. the medial arteries of the eyelids (aa.palpebrales mediales) are the terminal branches of the ophthalmic artery, go to the medial corner of the eye, anastomose with the lateral arteries of the eyelids (from the lacrimal artery) and form two arterial arches: the arch of the upper eyelid (arcus palpebralis superior) and the arch of the lower eyelid (arcus palpebralis inferior);
9. Dorsal nasal artery (a.dorsalis nasi) - the terminal branch of the ophthalmic artery, passes through the orbicularis muscle to the corner of the eye above the medial ligament of the palpebral artery, gives off branches to the lacrimal sac and passes to the bridge of the nose. This artery anastomoses with the angular artery (the terminal branch of the facial artery).

The anterior cerebral artery (a.cerebri anterior) branches off from the internal carotid artery slightly above the ophthalmic artery, passes forward over the optic nerve, converges with the artery of the same name on the opposite side and connects with it by a short unpaired anterior communicating artery (a.communicans anterior). Then the anterior cerebral artery turns upward on the medial surface of the cerebral hemisphere, lies in the groove of the corpus callosum, bends around the corpus callosum and goes towards the occipital lobe of the cerebrum. The artery supplies the medial side of the frontal, parietal and partly occipital lobes, as well as the olfactory bulbs, tracts and corpus striatum. The artery gives off two groups of branches to the brain matter - cortical and central (deep).

The middle cerebral artery (a.cerebri media) is the largest branch of the internal carotid artery. It goes laterally, into the deep lateral groove, follows the surface of the insular lobe (islet) and divides into its terminal branches, which supply the insula and the upper lateral parts of the frontal, temporal and parietal lobes of the cerebral hemisphere. The following parts are distinguished in the middle cerebral artery: the sphenoid part (pars sphenoidalis), adjacent to the greater wing of the sphenoid bone, the insular part (pars insularis) and the terminal (cortical) part (pars terminalis, s. pars corticalis).

The posterior communicating artery (a.communicans posterior) branches off from the internal carotid artery before the latter divides into the anterior and middle cerebral arteries. It runs posteriorly and slightly inward away from the pons and at its anterior edge it flows into the posterior cerebral artery (a branch of the basilar artery).

The anterior villous artery (a.choroidea anterior) is a thin vessel that branches off from the internal carotid artery behind the posterior communicating artery, runs posteriorly along the cerebral peduncle and approaches the posteroinferior parts of the temporal lobe. The artery enters the brain substance, branches in the walls of the inferior horn of the lateral ventricle, and participates in the formation of its vascular plexus. The anterior villous artery gives off branches to the optic tract, lateral geniculate body, internal capsule, basal ganglia, hypothalamic nuclei, and the red nucleus.

There are anastomoses between the branches of the internal and external carotid arteries, which play an important role in the distribution of blood in the head region.

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