Lateral view of the left carotid canal and carotid sheath at the C1 vertebral level. The cervical portion of the internal carotid artery has been reflected anteriorly exposing the internal carotid nerve and carotid sympathetic plexus within the petrous bone. Terminal branches of the external carotid artery visible here include the ascending pharyngeal artery, the occipital artery coursing posteriorly superficial to the carotid sheath, and the maxillary artery. The ascending pharyngeal artery has pharyngeal and neuromeningeal divisions. The neuromeningeal division consists of jugular and hypoglossal branches which supply neuromeningeal structures within their respective foramina. Cranial nerves IX, X and XI exit the skull via the jugular foramen. Cranial nerve XII courses inferiorly and crosses the internal carotid artery before turning anteriorly toward the tongue, while cranial nerve XI turns posteriorly and courses under the sternocleidomastoid. The vagus nerve runs within the carotid sheath. In this dissection, the transverse foramen of the axis (C2) is visible with the vertebral artery’s V3 segment running through it. (Image courtesy of AL Rhoton, Jr.)