Location and Vessel Topography
At its origin, the external carotid artery lies somewhat medial to the internal carotid artery. However, as it ascends, it crosses superficial to the internal carotid and comes to lie anterior to it.
Externally, the artery is securely covered by soft tissues: the platysma muscle and the superficial layer of the cervical fascia lie superficial to it. Laterally (external to the vessel), the parotid gland (glandula parotis) is adjacent to the artery.
Four major groups of branches arise from the main trunk, ensuring vascularization of various regions: anterior, posterior, medial, and terminal.
Anterior Group of Branches
This group supplies organs of the anterior neck region, the face, and the tongue. It includes three main vessels:
- Superior thyroid artery (a. thyroidea superior). Originates near the base of the external carotid artery, descending anteriorly toward the upper pole of the thyroid gland.
Its main branches:
- rr. glandulares anterior, posterior, lateralis — course to the thyroid lobes. They form important anastomoses with the inferior thyroid artery (derived from the thyrocervical trunk).
- r. infrahyoideus — supplies the infrahyoid muscles.
- r. sternocleidomastoideus — goes to the sternocleidomastoid muscle.
- a. laryngea superior — pierces the thyrohyoid membrane (membrana thyrohyoidea) and supplies the laryngeal tissues.
- Lingual artery (a. lingualis). Arises slightly superior to the superior thyroid artery. Sometimes it originates from a common trunk with the facial artery, termed the linguofacial trunk (truncus linguofacialis). The artery courses above the greater horn of the hyoid bone, running anteriorly and medially.
Branches:
- r. suprahyoideus — to the suprahyoid muscles.
- r. dorsales linguae — supply the palatine tonsil and the dorsum of the tongue.
- a. sublingualis — supplies the gingiva and sublingual salivary gland.
- a. profunda linguae — the terminal branch, runs within the thickness of the tongue to its apex and anastomoses with its counterpart from the opposite side.
- Facial artery (a. facialis). Arises superior to the lingual artery. Its pathway runs deep to the stylohyoid muscle and the posterior belly of the digastric muscle (m. digastricus). The vessel then enters the submandibular triangle directly through the substance of the submandibular salivary gland. After looping around the inferior border of the mandible, the artery emerges onto the face, supplying tissues from the angle of the mouth to the medial angle of the eye.
Its main branches: ascending palatine artery (a. palatina ascendens), submental artery (a. submentalis), superior and inferior labial arteries (aa. labiales superior et inferior), and angular artery (a. angularis).
Posterior Group of Branches
Vessels in this group course posteriorly, supplying the scalp of the occipital region and the auricle:
- Occipital artery (a. occipitalis). Arises at the level of the posterior belly of the m. digastricus and runs deep to the suboccipital muscles. It gives off branches to the sternocleidomastoid muscle (rr. sternocleidomastoidei), the posterior surface of the auricle (r. auricularis), and the dura mater (via the mastoid emissary vein opening as r. mastoideus, and via the parietal foramen as r. meningeus). Terminal branches (rr. occipitales) supply the skin and muscles of the occipital region.
- Posterior auricular artery (a. auricularis posterior). A small artery arising superior to the occipital artery (or via a common trunk with it). Ascends toward the mastoid process along the posterior margin of the auricle. It gives off the stylomastoid artery (a. stylomastoidea), auricular branch (r. auricularis), and occipital branch (r. occipitalis).
Medial Group of Branches
This group is represented by a single deep branch—the ascending pharyngeal artery (a. pharyngea ascendens). It arises directly from the medial wall of the external carotid artery and ascends along the lateral wall of the pharynx.
Its branches supply the pharynx (rr. pharyngeales), dura mater (a. meningea posterior), and tympanic cavity (a. tympanica inferior).
Note: The terminal branches of the external carotid artery form a separate, independent group that requires a detailed study of facial and temporal region topography.