General Medical Information

Arterial Supply

Susan D. John
Michael D. Maves

The two common carotid arteries differ in length because the right carotid usually arises from the brachycephalic artery behind the sternoclavicular joint, and the left arises from the arch of the aorta. Both arteries end by bifurcating into the internal and external carotid arteries. Over the lateral aspect of these arteries course the paired hypoglossal nerves. The internal carotid artery is situated more posteriorly and has no branches. The external carotid artery has branches and lies slightly anteriorly. This information can be crucial in differentiating the two vessels for ligation. From its origin, the internal carotid artery ascends directly toward the carotid canal and is crossed laterally, in ascending order, by the hypoglossal nerve, occipital artery, posterior belly of the digastric and associated stylohyoid muscle, and the posterior auricular artery. Still higher and close to the base of the skull, the external carotid artery is anterolateral to the internal carotid artery, and the stylopharyngeus muscle and associated glossopharyngeal nerve, the pharyngeal branch of the vagus, and the stylohyoid ligament all pass laterally to the internal carotid, between it and the external carotid artery.

After its origin in the carotid triangle, the external carotid artery passes upward, deep to the posterior belly of the digastric and stylohyoid muscles, crosses the styloglossus and the stylopharyngeus muscles on their lateral aspects, and parallel to the ramus of the mandible passes into the deeper portion of the parotid gland. The external carotid artery has branches to the superior thyroid, lingual, facial, ascending pharyngeal, occipital, posterior auricular, maxillary, transverse facial, and superficial temporal arteries.