IX-Glossopharyngeal

The Glossopharyngeal nerve is a mixed nerve, mainly composed of sensory fibres but also containing some parasympathetic and motor fibres.

Innervation

Sensory

• Pharynx
• Posterior one third of tongue
• Eustachian tube, middle ear
• Carotid body and carotid sinus

Motor

• Stylopharyngeus

Parasympathetic

• Parotid salivary gland

Function

Sensory

• General sensation in the pharynx, posterior third of tonge, Eustachian tube and middle ear
• Taste in posterior third of tongue and pharynx
• Chemoreception in carotid body and baroreception from carotid sinus

Motor

• Swallowing

Parasympathetic

• Salivation 

Anatomy

The glossopharyngeal nerve attaches to the brain stem in the rostral medulla via rootlets. In the brain stem the afferent fibres end in the trigeminal sensory nucleus, there are also connections with the nucleus ambiguus and the hypoglossal nucleus which are involved in the gag reflex. Whilst the majority of the afferent fibres end in the trigeminal sensory nucleus the taste fibres end in the nucleus solitarius.

The motor fibres arise from the nucleus ambiguus and go to the stylopharyngeus muscle, and the parasympathetic fibres originate in inferior salivatory nucleus before innervating the parotid salivary gland.