Neurology | Glossopharyngeal Nerve: Cranial Nerve IX

Описание: Official Ninja Nerd Website: https://ninjanerd.org

Ninja Nerds!
Join us in this lecture where Professor Zach Murphy will be discussing the anatomy and function of the glossopharyngeal nerve, cranial nerve IX. We begin by outlining its mixed composition—carrying sensory, motor, and parasympathetic fibers—and tracing its origin from the medulla oblongata. The lecture covers its course through the jugular foramen and the key branches that emerge along its path. We explore its sensory roles in taste from the posterior one-third of the tongue, somatic sensation from the oropharynx, middle ear, and Eustachian tube, and visceral sensation from the carotid body and sinus for baroreception and chemoreception.

We then examine the motor component, focusing on its innervation of the stylopharyngeus muscle, which elevates the pharynx during swallowing. The parasympathetic function is also discussed, detailing its contribution to the parotid gland via the lesser petrosal nerve and the otic ganglion. Connections to the nucleus ambiguus, solitary nucleus, and spinal trigeminal nucleus are explained to highlight how the glossopharyngeal nerve integrates into swallowing reflexes, gag reflex pathways, and autonomic cardiovascular regulation.

By connecting each functional modality to its clinical importance, we emphasize how lesions affecting cranial nerve IX can result in impaired gag reflex, loss of taste in the posterior tongue, dysphagia, and altered blood pressure reflexes. The lecture ties together the nerve’s structural anatomy with its diverse roles in sensory, motor, and autonomic regulation.

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