Intracranially, the brain is supplied by the internal carotid and vertebral arteries, which anastomose at the Circle of Willis. Extracranially, the external carotid artery supplies most structures of the face, scalp and neck.
The middle meningeal artery, a branch of the maxillary artery, is clinically important where it lies deep to the pterion, making it susceptible to damage causing an extradural haemorrhage in trauma.
Arterial Supply
The vertebral arteries enter via the foramen magnum and unite as the basilar artery, giving cerebellar branches before terminating as posterior cerebral arteries.
The internal carotid artery gives no branches in the head and neck and mainly supplies the brain. It enters the cranium via the carotid canal and forms part of the circle of Willis. It gives the following branches intracranially:
Ophthalmic artery
Posterior communicating artery
Choroidal artery
Anterior cerebral artery
Middle cerebral artery
The branches of the internal carotid artery can be remembered using the mnemonic Only Press Carotid Arteries Momentarily.
The majority of the blood supply to the head and neck is from the external carotid artery which gives off the following branches (in order):