One of the two divisions of the common carotid artery in the neck. The internal carotid supplies blood to much of the cerebral hemisphere, the eye, and the orbit. It begins at about the level of the top of the trachea, running up the side of the neck and entering the base of the skull through the carotid foramen, just in front of the jugular foramen. The internal carotid then turns forward and runs in the carotid canal inside the petrous part of the temporal bone. Passing over the foramen lacerum the internal carotid emerges from its canal and follows the carotid groove upward along the medial wall of the middle cranial fossa (passing through the cavernous sinus). Just below the optic nerve it loops back and turns upward to become the middle cerebral artery of the circle of Willis. As it passes the optic nerve, the internal carotid artery puts out its first branch, the ophthalmic artery. In the neck the internal carotid artery contains two receptor sites, the carotid body, a chemoreceptor for the oxygen concentration of the blood, and baroreceptors that detect and respond to arterial pressure.
Supplies blood to the brain, eyes, eyelids, forehead, nose, and internal ear.