Magnified view of anatomy at the level of the carotid bifurcation. The inferior end of the masseter muscle and submandibular gland are shown along the top edge of this image. The carotid sheath has been removed that encloses the internal jugular vein, internal and common carotid arteries, and the vagus nerve. The external carotid lies anterior to the internal carotid at their origins and quickly gives rise to the superior thyroid artery from its anterior border. The common facial vein, formed by union of the facial and anterior retromandibular veins, and the superior thyroid vein are tributary to the internal jugular. The spinal accessory nerve usually crosses the internal jugular vein superficially to enter the proximal portion of the sternocleidomastoid muscle, which it innervates. The external jugular vein is seen crossing the sternocleidomastoid obliquely to descend in the posterior or lateral cervical triangle. (Image courtesy of PA Rubino)