The neck
The neck occupies the space between the clavicles and thoracic inlet inferiorly, to the base of the skull and inferior border of the mandible superiorly. The cervical part of the vertebral column provides the support for the skull above and strength and movement to the neck proper. The anterior neck provides passage for the major neurovascular supply to and drainage from the head, neck and intracranial region, transmits the upper aerodigestive tract and houses the thyroid and parathyroid glands. In the posterior neck a large mass of extensor musculature is situated posterior to the cervical vertebrae. Cranial nerves nine through twelve descend into the neck: nine (glossopharyngeal) and twelve (hypoglossal) meander towards the oropharynx and tongue, respectively; cranial nerve eleven (accessory) deflects backwards to supply the sternocleidomastoid and trapezius muscles whilst the tenth cranial nerve (vagus) wanders inferiorly within the carotid sheath between and posterior to the common carotid artery and internal jugular vein, before disappearing into the thoracic and abdominal cavities.