external carotid artery

The external carotid artery (ECA) is one of the two terminal branches of the common carotid artery. The other terminal branch is the internal carotid (ICA), which is somewhat larger than the ECA.

Summary

Gross anatomy

Origin and course

The ECA begins at the level of the upper border of the thyroid cartilage (at the level of the fourth cervical vertebra). It takes a slightly curved course upwards and anteriorly before inclining backwards to the space behind the neck of the mandible. Along its course, it rapidly diminishes in size and as it does so, gives off various branches (see below). As it enters the parotid gland, it gives rise to its terminal branches, the superficial temporal and maxillary arteries.

Branches

The branches of the external carotid artery can be subdivided into groups:

Memorable mnemonics for these branches include:

  • Some Anatomists Like Freaking Out Poor Medical Students
  • Some American Ladies Found Our Pyramids Most Satisfactory
Relations

Variant anatomy

  • variations in origin arise from the anomalous bifurcation of the common carotid artery - bifurcations may commonly be seen at the level of the cricoid cartilage (C5 level) or at the hyoid bone (C2 level)
  • variant branching patterns
    • linguofacial trunk (incidence ~20%): common origin lingual and facial arteries
    • thyrolingual trunk (incidence ~2.5%): common origin superior thyroid and lingual arteries
    • thyrolinguofacial trunk (incidence ~2.5%): common origin superior thyroid, lingual and facial arteries
    • common occipito-auricular trunk (incidence ~12.5%): common origin occipital and posterior auricular arteries