The internal carotid artery runs up each side of the neck from the fork of the common carotid, at about the fourth neck vertebra, enters the skull through the carotid canal, passes through the cavernous sinus beside the pituitary gland and ends under the brain, at the inner end of the lateral fissure, by dividing into the anterior and middle cerebral arteries. [1]
The 3D brain needs JavaScript. The text below still says where the internal carotid artery is and what it does.
Opens with the blood-supply layer on (about 0.8 MB) and a front (coronal) slice, so the two arteries are seen rising under the brain, either side of the midline, and bending forward at the top. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Lit: the left and right internal carotid arteries from the height of the foramen magnum (the lowest point of the medulla) up — about 70 mm of each: the last of the climb through the skull base, slanting inward, then the forward bend beside the pituitary and the end under the brain where the anterior and middle cerebral arteries leave it. The part in the neck below that height is cut off in this model. Every other artery shows in a darker colour. [2][1]
It begins in the neck where the common carotid artery divides, around the level of the fourth cervical vertebra, and climbs in the carotid sheath with no branches in the neck. [1]
It enters the skull through the carotid canal in the petrous part of the temporal bone, then runs inside the cavernous sinus beside the body of the sphenoid bone, with the abducens nerve on its outer side; its S-shaped curve there is called the carotid siphon. [1]
Leaving the sinus beside the anterior clinoid process, it runs alongside the optic nerve, then passes between the optic and oculomotor nerves to the anterior perforated substance, at the inner end of the lateral fissure. [1]
Its course is named in seven segments, C1 to C7: cervical, petrous, lacerum, cavernous, clinoid, ophthalmic and communicating. [1]
Its very end (the carotid terminus) is one of the links of the circle of Willis, between the posterior communicating artery and the first part of the anterior cerebral artery. [3]
What it does
It supplies the brain, including the eyes; the external carotid, its partner in the neck, supplies the face, scalp, skull and meninges instead. [1]
It ends by dividing into the anterior and middle cerebral arteries, which together supply most of the frontal, parietal and temporal lobes. [1][4][5]
Just before that split it gives off the posterior communicating artery, linking it to the posterior cerebral artery, and the anterior choroidal artery. [1]
Its ophthalmic artery, the first branch after the cavernous sinus, runs through the optic canal under the optic nerve; its branches supply the eyeball and the other structures of the eye socket. [6]
Its superior and inferior hypophyseal branches feed the pituitary gland, and branches climbing the pituitary stalk supply the middle of the optic chiasm. [1][7]
The anterior choroidal artery supplies the choroid plexus of the lateral and third ventricles, the optic tract, part of the internal capsule, the globus pallidus, the amygdala and the hippocampus. [8]
Other names
Latin: arteria carotis interna, often shortened to ICA. With its partner on the other side it is the front (carotid) supply of the brain, beside the back (vertebral–basilar) supply. [1][9]
Size
On this model the left and right internal carotid arteries (from the height of the foramen magnum up) fit in a box about 21 mm front to back, 60 mm side to side and 71 mm top to bottom (the box they fit in, not their volume). [2]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.