Carotid Body and Carotid Sinus

Most cranial and spinal nerves contain efferent and afferent vascular fibers. The oculomotor (III), trigeminal (V), facial (VII), vagus (X), glossopharyngeal (XI), phrenic, ulnar, median, pudendal, and tibial nerves contain relatively large numbers of vascular fibers. Accordingly, lesions involving these nerves are more likely to produce vasomotor and other autonomic disturbances. Vascular disorders are usually more evident in peripheral arteries and arterioles (like those in the fingers and toes) and in arteriovenous anastomoses because they have thicker muscular layers and a richer innervation than larger arteries, which have more elastic tissue in their walls. Arteries supplying erectile tissues and the skin are also richly innervated, whereas the nerve supply to veins and venules is comparatively sparse. Nerve fibers are often associated with capillaries, but their functions are unknown.

Carotid Sinus and Carotid Body. The carotid sinus is a dilation in at the beginning of the internal carotid artery; the tunica media is thin, and adventia are thicker with multiple terminations of the glossopharyngeal nerve. The carotid sinus serves as a baroreceptor and plays an important role in the control of intracranial blood pressure. The carotid body is a small reddish brown structure behind the bifurcation of the common carotid artery and is a chemoreceptor.

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