Corpus: Glossopharyngeal nerve

The glossopharyngeal nerve is the 9th cranial nerve and provides motor innervation to the pharyngeal muscles with special visceromotor fibers. It also carries general somatosensory, general visceromotor, general viscerosensory and special viscerosensory fibers.

The glossopharyngeal nerve is categorized as a branchial arch nerve and develops from the nerve of the third branchial arch. Consequently, it innervates all muscles that originate from the muscle anlage of this branchial arch.

The glossopharyngeal nerve emerges laterally from the medulla oblongata and then passes through the jugular foramen. The purely sensory superior ganglion is formed at the base of the skull. Additionally, the mixed sensory inferior ganglion is formed below the jugular foramen.

The glossopharyngeal nerve then runs downward along the back of the stylopharyngeus muscle and is located anterolateral to the internal carotid artery. Between the stylopharyngeus muscle and the styloglossus muscle, it continues downward to the posterior part of the tongue, where it divides into its terminal branches.

4.1. Tympanic nerve

The tympanic nerve arises from the inferior ganglion. It contains general somatosensory and parasympathetic fibers. The parasympathetic fibers pass through the ganglion without synapsing. This nerve supplies general sensory fibers to the middle ear and eustachian tube, and secretory fibers to the parotid gland via the otic ganglion.

4.2. Carotid sinus branch (Ramus sinus carotici)

The carotid sinus branch supplies the chemoreceptors of the carotid body and the baroreceptors of the carotid sinus with general visceral sensory fibers.

4.3. Pharyngeal branches (Rami pharyngei)

The pharyngeal branches innervate the pharyngeal muscles, much of the soft palate muscles, the glands of the pharynx, and the pharyngeal mucosa. They form the pharyngeal plexus in conjunction with fibers from the vagus nerve.

4.4. Lingual branches (Rami linguales)

The lingual branches terminal branches carry general sensory and special sensory fibers for the posterior third of the tongue.

4.5. Tonsillar branches (Rami tonsillares)

The tonsillar branches synapse in the otic ganglion and supply the palatine tonsil and its mucosa.

4.6. Branch to stylopharyngeus muscle (Ramus musculi stylopharyngei)

This branch supplies the stylopharyngeal muscle.

4.7. Communicating branch with the auricular branch of the vagus nerve (Ramus communicans cum ramo auriculare nervi vagi)

This branch is a small connecting branch to the auricular branch of the vagus nerve.

5.1. General somatosensory fibers

The nucleus for these fibers is the spinal trigeminal nucleus, located in the medulla oblongata and spinal cord.

5.2. General visceromotor fibers

The nucleus of these fibers is called the inferior salivatory nucleus, located at the junction of the pons and medulla oblongata.

5.3. Special visceromotor fibers

The nucleus for these fibers is the nucleus ambiguus, located in the medulla oblongata.

5.4. General and specific visceromotor fibers

These fibers terminate in the solitary nucleus, also found in the medulla oblongata.

6.1. Nerve dysfunction

Isolated dysfunction of the glossopharyngeal nerve is rare. It often involves the vagus and accessory nerves, which also pass through the jugular foramen. Loss of function results in a lack of sensory innervation to the pharynx, eliminating the gag reflex. Other symptoms include loss of taste sensation in the posterior third of the tongue and deviation of the soft palate to the healthy side. Dysfunction of the pharyngeal branches can cause food to escape through the nose during swallowing.

Joint loss with the vagus nerve can occur in conditions like Avellis-Longhi syndrome.

6.2. Neuralgia

Glossopharyngeal neuralgia, also known as Collet-Sicard syndrome, is characterized by intermittent pain in the palatal arch, triggered by actions like swallowing, speaking loudly, or yawning. The pain radiates to the tongue, jaw angle, and neck region.