What are the branches of the external and internal carotid arteries?

Branches of the External and Internal Carotid Arteries

External Carotid Artery Branches

The external carotid artery typically gives rise to eight major branches that supply the face, neck, and superficial head structures. 1

Anterior Branches

• Superior thyroid artery - originates most commonly directly from the external carotid artery (51.2% of cases), though it can arise from the bifurcation of the common carotid artery (45.3%) or from the common carotid itself (3.5%) 2
• Lingual artery - supplies the tongue and floor of mouth 3, 2
• Facial artery - supplies facial structures 3, 2

Posterior Branches

• Ascending pharyngeal artery - supplies pharyngeal structures 3, 4
• Occipital artery - supplies posterior scalp and connects to the vertebral artery as an important collateral pathway 1, 3
• Posterior auricular artery - supplies structures around the ear 5, 6

Terminal Branches

• Maxillary artery - the larger terminal branch that supplies deep facial structures, including the maxillary sinus region through three main subdivisions: infraorbital artery, posterior superior alveolar artery, and posterior lateral nasal artery 1, 7, 5
• Superficial temporal artery - the smaller terminal branch that supplies the temporal region and serves as a collateral pathway to the ophthalmic branches of the internal carotid artery 1, 5

Common Anatomical Variations

• In 77.8% of cases, the superior thyroid, lingual, and facial arteries originate separately 2
• A linguofacial trunk (combined lingual and facial origin) occurs in approximately 19.9% of cases 3, 2
• A thyrolingual trunk is rare, occurring in only 2.8% of cases 2
• An occipitoauricular trunk (combined occipital and posterior auricular origin) can occur 6

Internal Carotid Artery Branches

The internal carotid artery has no branches in its cervical (extracranial) portion, but gives rise to critical intracranial branches after entering the skull. 1

Intracranial Branches

• Ophthalmic artery - arises near where the internal carotid enters the subarachnoid space at the base of the skull; receives collateral flow from external carotid branches (superficial temporal and internal maxillary arteries) 1
• Posterior communicating artery - connects the internal carotid system to the vertebrobasilar circulation through the circle of Willis 1
• Anterior cerebral artery - one of two terminal branches; connects to the contralateral side via the anterior communicating artery 1
• Middle cerebral artery - the other terminal branch; the largest branch supplying the cerebral hemispheres 1

Clinical Significance of Collateral Pathways

Understanding the collateral connections between external and internal carotid systems is critical for predicting outcomes in carotid occlusive disease. 1

Major Collateral Routes

• External to internal carotid: via internal maxillary and superficial temporal arteries connecting to ophthalmic artery branches 1
• External carotid to vertebral artery: via the occipital branch 1
• Between hemispheres: via the anterior communicating artery connecting left and right internal carotid territories 1
• Vertebrobasilar to internal carotid: via the posterior communicating artery 1

Important Caveats

• The circle of Willis is complete in fewer than 50% of individuals, limiting collateral capacity in many patients 1
• The internal carotid artery shows significant anatomical variation, with undulation, coiling, or kinking in up to 35% of cases, particularly in elderly patients 1
• The common carotid typically bifurcates at the level of the thyroid cartilage, but anomalous bifurcations can occur up to 5 cm higher or lower 1