External Carotid Artery and its Branches

The external carotid artery is one of the two main divisions of the common carotid artery. It stems from the aortic arch on the left side and from the brachiocephalic artery on the right side. it climbs the lateral sides of the neck within the carotid sheath, which is found just behind the sternocleidomastoid muscle.

The carotid bifurcation occurs at the level of the thyroid cartilage in the larynx. The external carotid artery is the only division of the common carotid that gives branches to the neck region and supplies the external structures of the head and face.

This article will discuss the course and the anatomy of the external carotid artery.

Borders & Relations

Medially the hyoid bone, the wall of the pharynx, the superior laryngeal nerve and the parotid gland surround the artery. Laterally, the internal carotid artery passes by in the initial phase of the external carotid artery, along with the superior laryngeal nerve posteroinferiorly.

Posterosuperiorly however, the internal and external branches of the carotid are separated by the: styloglossus muscle, the stylopharyngeus muscle, the glossopharyngeal nerve (CN IX), the pharyngeal branch of the vagus nerve (CN X), part of the parotid gland.

Anteriorly, the artery is covered by the skin, the superficial fascia, the platysma, the deep cervical fascia and the sternocleidomastoid muscle.

The nerves, vasculature and musculature that cross over the external carotid artery during its journey include the: hypoglossal nerve (CN XII), lingual nerve, ranine vein, the common facial nerve, superior thyroid veins, digastric muscle, the stylohyoid muscle, the parotid gland, the deep facial nerve, the temporal vein, internal maxillary veins.

Branches

Superior Thyroid Artery

The superior thyroid artery (S) is the origin of the superior laryngeal artery that supplies the larynx. The main artery also supplies the thyroid gland, infrahyoid muscles and the sternocleidomastoid muscle.

Ascending Pharyngeal Artery

The ascending pharyngeal artery (A) ascends superiorly along the pharynx, while branching off to the pharynx, prevertebral muscles, the middle ear and the cranial meninges.

Lingual Artery

The lingual artery (L) is covered by the hypoglossal nerve (CN XII), the stylohyoid muscle and the posterior belly of the digastric muscle. It runs beneath the hyoglossus muscles and branches into the deep lingual and sublingual arteries which supply the intrinsic muscles of the tongue and the floor of the mouth.

Facial Artery

The facial artery (F) runs around the middle of the mandible before it enters the face, where it gives branches to the tonsils, palate and the submandibular glands.

Occipital Artery

The occipital artery (O) supplies the posterior region of the scalp and grooves the base of the skull as it travels. Initially it passes deep to the posterior belly of the digastric muscle.

Posterior Auricular Artery

The posterior auricular artery (P) runs behind the external acoustic meatus and the mastoid process, separating the two structures. It supplies the adjacent musculature, the parotid gland, the facial nerve (CN VII), the ear and the scalp.

Maxillary Artery

The maxillary artery (M) is the larger of the two terminal branches which can precede one another depending on which anatomist you ask. Its branches supply:

• the external acoustic meatus
• the tympanic membrane
• the dura mater
• the calvaria
• the mandible
• the gingivae
• the teeth
• the temporal muscle
• the pterygoid muscle
• the masseter muscle 
• the buccinator muscle

Superficial Temporal Artery

The superficial temporal artery (S) supplies only the temporal region of the scalp, as it is the smaller terminal branch and does not have additional named branches or divisions.

Mnemonics

If one looks back to the section of this article termed ‘Branches’, each major artery has been assigned a letter, which corresponds to the first letter of a word in each mnemonic. The order of arteries listed corresponds to the order they branch off from the external carotid artery as it ascends and follows the order of the words in each mnemonic. There are three different mnemonics, of which only one is needed in order to remember the branches.

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