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Magnified Dissection View of the Area Around the Bifurcation of the Left Common Carotid Artery

Surgical Correlation


Magnified dissection view of the area around the bifurcation of the left common carotid artery. The common carotid artery divides in the adult at about the C4 vertebral level or at the upper border of the thyroid cartilage of the larynx. The internal carotid artery provides no branches in the neck. The ascending pharyngeal artery usually arises from the medial surface of the external carotid at its origin. The external carotid quickly gives rise to the superior thyroid from its anterior border, which descends on the inferior pharyngeal constrictor muscle enroute to the thyroid gland. Proximally, the superior thyroid gives rise to the superior laryngeal artery, which passes through the thyrohyoid membrane in company with the internal laryngeal nerve. These supply the upper part of the laryngeal interior. The hypoglossal nerve descends deep to the posterior digastric muscle. Near the origin of the occipital branch of the external carotid it courses forward toward the oral cavity superficial to the hyoglossus muscle and then deep to the mylohyoid before entering the tongue where it provides motor innervation to intrinsic and extrinsic muscles, except palatoglossus. C1 spinal nerve fibers leave the epineurial sheath of the hypoglossal nerve as the superior root of the ansa cervicalis to supply infrahyoid muscles. The styloglossus muscle can be seen entering the superolateral border of the tongue where it interdigitates with the hyoglossus. The nearby glossopharyngeal nerve is coursing to enter the oropharynx to provide sensory innervation to it and the posterior third of the tongue mucosa. Superior to the bifurcation of the common carotid can be seen the carotid sinus nerve, a sensory branch of the glossopharyngeal nerve. It innervates the baroreceptors of the carotid sinus and the chemoreceptors of the carotid body. Removal of deep neck musculature has exposed the suboccipital muscle, obliquus capitis inferior. A portion of the vertebral artery is shown before it enters the transverse foramen of the atlas. It is crossed superficially by the ventral ramus of the C2 spinal nerve. (Image courtesy of PA Rubino)