*For more about the circle of Willis and blood supply to the brain, please see intracranial blood supply

All arterial supply to the head and neck occurs via the common carotid and vertebral arteries.

Common carotid artery

The right common carotid artery branches from brachiocephalic artery (a branch of the aorta) while the left common carotid artery branches directly from the aorta. Each travel upwards in a carotid sheath (alongside the vagus nerve and internal jugular vein) before splitting at the level of the superior border of the laryngeal thyroid cartilage into the internal and external carotid arteries. The internal carotid artery continue up the sheath and enters the cranial cavity via the carotid canal to feed into the circle of Willis that supplies the brain. Meanwhile, the external exits the sheath primarily to supply the neck, face and meninges.

Vertebral artery

The vertebral arteries are a branch of the subclavian arteries and travel upwards through the transverse foramina of the cervical vertebrae (generally starting from C6). Exiting the transverse foramina of the atlas (C1), it bends posteriorly and grooves the vertebra before turning upwards to enter the foramen magnum at the base the skull. The left and right arteries gives off a few branches (such as to the posterior meninges), before fusing to form the basilar artery ventral to the brainstem. The basilar artery feeds into the circle of Willis that supplies the brain.