External carotid artery

The external carotid artery is a terminal branch of the common carotid artery that supplies blood to the face, scalp, jaw, neck, oral cavity, and parts of the pharynx and larynx. It gives rise to several important branches and serves as the primary arterial supply to many superficial and deep structures of the head and neck.

Location

The external carotid artery originates in the neck at the level of the C3–C4 vertebrae, typically at the upper border of the thyroid cartilage, where the common carotid bifurcates into internal and external carotid arteries. It ascends in the carotid triangle, anterior and medial to the internal carotid artery initially, then passes deep to the posterior belly of the digastric and stylohyoid muscles to enter the parotid gland.

Origin

• Parent vessel: Common carotid artery
• Level of origin: Upper border of the thyroid cartilage (C3–C4)

Course

The external carotid artery ascends within the carotid triangle, medial to the internal jugular vein and anterior to the internal carotid artery. It travels deep to the posterior belly of the digastric and stylohyoid muscles and enters the parotid gland, where it divides into its two terminal branches: the maxillary artery and the superficial temporal artery.

Branches

The external carotid artery gives off eight branches — six arise in the neck and two are terminal branches:

Anterior Branches

• Superior thyroid artery: Supplies the thyroid gland, larynx, and infrahyoid muscles
• Lingual artery: Supplies the tongue, floor of the mouth, and sublingual gland
• Facial artery: Supplies the face, soft palate, tonsils, and submandibular gland

Posterior Branches

• Occipital artery: Supplies the posterior scalp and sternocleidomastoid muscle
• Posterior auricular artery: Supplies the auricle and scalp posterior to the ear

Medial Branch

• Ascending pharyngeal artery: Supplies the pharynx, prevertebral muscles, middle ear, and meninges

Terminal Branches

• Maxillary artery: Supplies deep structures of the face including the maxilla, mandible, dura mater, nasal cavity, and muscles of mastication
• Superficial temporal artery: Supplies the scalp in the temporal region

Relations

• Medial: Pharynx, superior laryngeal nerve
• Lateral: Internal jugular vein, parotid gland (superiorly)
• Posterior: Internal carotid artery (initially), styloid process
• Anterior: Digastric and stylohyoid muscles

Function

The external carotid artery is responsible for the arterial supply of most superficial and deep structures of the head and neck excluding the brain and orbit, which are supplied by the internal carotid artery.

Blood Supply and Drainage

• Supplies: Face, scalp, tongue, pharynx, larynx, thyroid gland, jaw, and meninges
• Drained by: Facial, retromandibular, and external jugular veins

Innervation of Associated Structures

Although the external carotid artery itself is not innervated in the typical sense, the tissues it supplies are innervated by cranial nerves including:

• Facial nerve (CN VII)
• Glossopharyngeal nerve (CN IX)
• Vagus nerve (CN X)
• Trigeminal nerve branches (CN V)

Clinical Relevance

• Facial trauma or surgery: Risk of bleeding due to damage to branches like the facial or maxillary artery
• Carotid endarterectomy: Procedure typically spares the external carotid artery unless stenosed
• Temporal arteritis: Affects the superficial temporal artery, a terminal branch of the external carotid
• Parotid gland surgery: The external carotid and its branches lie within or near the gland, increasing surgical risk