The carotid artery is a major artery of the head and neck that supplies blood to the head and neck. There is a left and right carotid artery.
Where they first arise, the carotid arteries are known as common carotid arteries. The left carotid arises from the arch of aorta, while the right carotid arises as one of the branches of the bifurcation of the brachiocephalic artery (trunk) into the carotid and right subclavian artery. They then normally continue along similar paths.
At approximately the level of the third cervical vertebra, the common carotid branches into the internal and external carotid arteries.
It is in relation, behind, with the Longus capitis, the superior cervical ganglion of the sympathetic trunk, and the superior laryngeal nerve; laterally, with the internal jugular vein and vagus nerve, the nerve lying on a plane posterior to the artery; medially, with the pharynx, superior laryngeal nerve, and ascending pharyngeal artery.
The artery is separated from the bony wall of the carotid canal by a prolongation of dura mater, and is surrounded by a number of small veins and by filaments of the carotid plexus, derived from the ascending branch of the superior cervical ganglion of the sympathetic trunk.
As the artery crosses the optic nerve it is accompanied by the nasociliary nerve, and is separated from the frontal nerve by the Rectus superior and Levator palpebræ superioris.
The two largest are the two internalcarotidarteries, the left and right branches of the common carotidarteries in the neck which enter the skull, as opposed to the external carotid branches which supply the facial tissues.
Both internalcarotidarteries, within and along the floor of the cerebral vault, are interconnected via the anterior communicating artery.
In case one of the supply arteries is occluded, the Circle of Willis provides interconnections between the internalcarotidarteries and basilar artery along the floor of the cerebral vault, providing blood to tissues that would otherwise become ischemic.