All the arteries of the human brain originate from the internal carotid artery and the basilar artery, which are big-caliber blood vessels that supply the cerebrum and cerebelum with vital oxygen-rich blood, which is pumped by the left ventricle of the heart.
The carotid artery (right and left) arises from the common carotid on both sides of the neck. Then, it runs deeply up into the head. At the level of the orbit (eye socket), it gives off a branch that supplies the eyeball; it is the ophthalmic artery. Then, it keeps traveling up for about 1 cm to divide into the anterior cerebral, middle cerebral, and posterior communicating arteries, which anastomose (join) the posterior cerebral artery to make up the circle of Willis in the base of the brain. The anterior, middle, and posterior cerebral arteries go up in the brain, giving off branches throughout the cerebral cortex as they go.
Meanwhile, the basilar artery arises from the anastomose of the left and right vertebral arteries, at the level of the junction of the medalla oblongota and the pons. Then, it runs up anteriorly to divide into the right and left posterior cerebral arteries, which join the circle of Willis. In its short course, the basilar artery gives off the pontine arteries, which supply the pons, and the anterior inferior and the superior cerebellar arteries, which provides the cerebellum with oxygen-rich blood.