Carotid artery

Any of the main arteries of the neck and head. There are 2 common carotid arteries (left and right), each of which divides into 2 main branches (internal and external). The left carotid arises from the aorta and runs up the neck on the left side of the trachea (windpipe). The right carotid arises from the subclavian artery (which branches off the aorta) and follows a similar route on the right side of the neck. Just above the level of the larynx (voice-box), each carotid artery divides to form an external carotid artery and an internal carotid artery. The external arteries have multiple branches that supply most tissues in the face, scalp, mouth, and jaws; the internal arteries enter the skull to supply the brain and eyes. At the base of the brain, branches of the 2 internal carotids and the basilar artery join to form a ring of vessels called the circle of Willis. Narrowing of these vessels may be associated with transient ischaemic attack (TIA); obstruction of them causes a stroke.