Neurovasculature of head & neck
The blood supply of the head and neck is mainly received by the carotid and vertebral arteries. The right common carotid originates from the bifurcation of the brachiocephalic trunk, while its left counterpart branches directly from the arch of aorta. At the level of the fourth cervical vertebra (C4), the carotids divide into the external and internal carotid arteries.
The external carotid artery supplies the areas of the head and neck external to the skull. It ascends in the neck, behind the mandible and anterior to the ear lobule. The external carotid divides into superficial temporal and maxillary arteries at the level of the parotid gland. Before its termination, the external carotid gives off several branches and they are: the superior thyroid, lingual, facial, ascending pharyngeal, occipital and posterior auricular arteries.
The internal carotid artery does not supply any structures within the neck; instead it supplies the brain, eyes, and forehead within the cranial cavity.
Both the right and left vertebral arteries originate from the subclavian arteries. They travel up the posterior aspect of the neck and enter the cranial cavity through the foramen magnum. Vertebral arteries give rise to the basilar arteries that supply the brain. The neck region is supplied by other arteries besides the carotids, those of which arise from the thyrocervical trunk. They are the inferior thyroid, ascending cervical, transverse cervical and the suprascapular arteries.
The venous drainage of the head and neck collect deoxygenated blood to return to the heart. It can be divided into three parts: that of the brain and meninges; the scalp and face; and the neck. The brain and its meninges are drained by the dural venous sinuses. The face and scalp veins follow their associated arteries and bear their name, and then drain into the internal and external jugular veins. The neck's drainage is supplied by the anterior jugular veins.
The external jugular vein is formed by the joining of the posterior auricular and retromandibular veins. It has various tributaries throughout its course and drains into the subclavian vein.
The anterior jugular veins are paired veins that drain into the subclavian too and communicate via the jugular venous arch. The internal jugular vein, on the other hand, joins the subclavian to form the brachiocephalic vein. It receives blood from the facial, lingual, occipital, superior and middle thyroid veins. The dural venous sinuses are spaces present between the periosteal and meningeal layers of the dura mater. They retrieve blood from veins draining the brain and skull to ultimately empty into the internal jugular vein.
The head and neck are innervated by the major cranial and spinal nerves. They connect the central nervous system to the other organs, skin and muscles of the head, and neck. There are 12 pairs of cranial nerves that arise from different parts of the brain. They provide innervation for the sensory organs, in addition to the muscles of the head and neck.
The spinal cord is the most important connection between the brain and body. It carries the signals that are not provided by the cranial nerves to and from the brain. Eight spinal nerves extend from the spinal cord in the neck to form the cervical plexus (C1-C4). The nerves originating from the cervical plexus supply the back of the head, in addition to some of the muscles in the neck.