External Carotid Artery

Overview

The external carotid artery is a major artery of the head and neck

Origin

Arises at the bifurcation of the common carotid artery at the level of the upper border of the thyroid cartilage (level of C4). It lies against the sidewall of the pharynx, anteromedial to the internal carotid artery.

Course

• Ascends anterior to the internal carotid artery, deep to the posterior belly of digastric and stylohyoid.
• Pierces parotid fascia entering the parotid gland.
• Divides within the parotid gland behind the neck of the mandible (surface marking: in front of tragus) into terminal branches; superficial temporal and maxillary arteries.

Branches

• Superior thyroid artery
  • Course: Arises at the commencement of external carotid, runs vertically down alongside larynx (with vein) to the upper pole of the thyroid gland.
  • Branches: Infrahyoid, sternocleidomastoid, superior laryngeal and cricothyroid.
  • Supplies: Thyroid gland and larynx
• Ascending pharyngeal artery
  • Course: Arises from the back of external carotid, near the bifurcation of the common carotid and ascends between internal carotid artery and side of the pharynx, to the undersurface of the skull base, lying on the longus capitis
  • Supplies: Pharynx
• Lingual artery
  • Course: Arises from the front of external carotid artery above superior thyroid
  • Supplies: Tongue, sublingual gland, gingiva and oral mucosa
• Facial artery
  • Course: Arises from the front of the external carotid artery, above lingual, running upwards on the superior constrictor, deep to digastric and stylohyoid muscles.
  • Supplies: Palatine tonsils, soft palate, pterygoid, mylohyoid, digastric muscle, submandibular gland, muscles and skin of the face.
• Occipital artery
  • Course: Arises from the back of the external carotid, level with the facial artery. Courses deep to the lower border of the posterior belly of the digastric muscle
  • Supplies: Back of scalp, sternocleidomastoid, deep muscles in the back and neck
• Posterior auricular artery
  • Course: Arises above the level of digastric, coursing upwards superficially to the styloid process.
  • Supplies: Scalp and ear
• Maxillary artery
• Superficial temporal artery

Relations

• Internal jugular vein – Near origin, lies medial to internal jugular vein. Towards terminal end, lies anterior and superficial to internal jugular vein
• Anteromedial to internal cartoid artery
• Superficial:
  • Covered by skin, superficial fascia, platysma, deep fascia, and anterior margin of the sternocleidomastoid
  • Crossed by the hypoglossal nerve, by the lingual, ranine, common facial, and superior thyroid veins; and by the digastricus and stylohyoideus
  • Higher up it passes deeply into the substance of the parotid gland, where it lies deep to the facial nerve and the junction of the temporal and internal maxillary veins.
• Medial: hyoid bone, the wall of the pharynx, the superior laryngeal nerve, and a portion of the parotid gland.
• Lateral: in the lower part of its course, is the internal carotid artery.
• Posterior: near its origin, the superior laryngeal nerve; and higher up, it is separated from the internal carotid artery by the styloglossus and stylopharyngeus, the glossopharyngeal nerve, the pharyngeal branch of the vagus nerve, and part of the parotid gland.

Anatomical Variants

• Anomalous bifurcation of the common carotid artery – commonly cricoid cartilage (C5 level) or hyoid bone (C2 level)
• Variable branching pattern:
  • Linguofacial trunk
  • Thyrolingual trunk
  • Occipito-auricular trunk

Clinical significance

Carotid pulse can be palpated between trachea and lower larynx medially and sternocleidomastoid laterally. This action presses the artery against the anterior tubercle of transverse process of C6 vertebra.