Carotid arterial tree anatomy and relationships. The left common carotid artery is shown dividing into its internal carotid and external carotid branches. The internal carotid artery, unlike the external carotid, gives rise to no branches in the neck. Near the origin of the ECA on its medial side is the ascending pharyngeal artery ascending deep in the neck. The occipital and posterior auricular arteries are branches that come off the posterior surface of the ECA. The other branches arise from its anterior border. The superior thyroid artery descends posterior and then deep to the thyrohyoid muscle to the upper border of the thyroid gland. It typically gives rise to a smaller superior laryngeal artery that passes through the thyrohyoid membrane in company with the internal laryngeal nerve to supply the upper interior of the larynx. The lingual artery arises from the ECA near the tip of the great horn of the hyoid bone and passes into the oral cavity deep to the hyoglossus muscle. The facial artery courses superficial to the hyoglossus and on the deep surface of the submandibular gland (not present) before emerging onto the face. The ECA terminates as the superficial temporal and maxillary arteries near the neck of the mandible. The maxillary artery is shown here giving off the inferior alveolar and middle meningeal arteries. The lingual and inferior alveolar nerves are branches of the mandibular nerve and emerge between the lower border of the lateral pterygoid and the medial pterygoid muscles. The inferior alveolar gives rise to a motor branch, the mylohyoid nerve, which supplies the mylohyoid and anterior digastric muscles. The auriculotemporal nerve is also shown, but has been moved from its normal horizontal relationship and exit out of the infratemporal fossa behind the neck of the mandible. The internal jugular vein has been cut and reflected to show portions of the glossopharyngeal, vagus, hypoglossal, and spinal accessory nerves descending in the neck. The hypoglossal nerve courses forward near the origin of the occipital artery passing superficial to the hyoglossus muscle before entering the floor of the mouth deep to the mylohyoid muscle. The superior root of the ansa cervicalis (containing C1 nerve fibers) leaves the epineurial sheath of the hypoglossal and descends in the neck where it unites with the inferior root to supply motor innervation to most of the infrahyoid muscles. (Image courtesy of PA Rubino)