Medicine & USMLE

Glossopharyngeal Nerve (CN IX)

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Cranial Nerves
  1. Olfactory Nerve (CN I)
  2. Optic Nerve (CN II)
  3. Oculomotor Nerve (CN III)
  4. Trochlear Nerve (CN IV)
  5. Trigeminal Nerve (CN V)
  6. Abducens Nerve (CN VI)
  7. Facial Nerve (CN VII)
  8. Vestibulocochlear Nerve (CN VIII)
  9. Glossopharyngeal Nerve (CN IX)
  10. Vagus Nerve (CN X)
  11. Accessory Nerve (CN XI)
  12. Hypoglossal Nerve (CN XII)

Summary

The glossopharyngeal nerve, also known as cranial nerve number 9 (CN IX) or the ninth cranial nerve, is a nerve that carries both motor and sensory information. It sends outgoing motor commands that enable swallowing and salivation. It also carries inbound sensory information from taste buds and sensory receptors in the posterior third of our tongue. Additionally, it carries sensory information from our upper oropharynx, which is used as a sensory component of the gag reflex, as well as sensation from the tonsils and middle ear cavity. The glossopharyngeal nerve also carries sensory information from chemo and baroreceptors in our carotid body, which helps maintain proper blood composition and pressure. Anatomically, the glossopharyngeal nerve originates from the brainstem at the level of the medulla and exits our skull through the jugular foramen.

Key Points

  • Glossopharyngeal Nerve (Cranial Nerve IX)
    • Nerve type
      • Motor
      • Sensory
    • Function
      • Swallowing
        • Elevates of pharynx/larynx via control of stylopharyngeus muscle
        • Test by asking patient to swallow
      • Taste (taste buds) and sensation from posterior ⅓ of tongue
      • Sensation
        • Upper oropharynx
          • Contributes to gag reflex
        • Tonsillar region (can think of near posterior tongue)
        • Middle ear cavity, tympanic membrane (inner surface), eustachian tube
      • Salivation
        • Carries parasympathetic innervation of parotid gland
          • Via otic ganglion
      • Carotid body/sinus chemo/baroreceptors
        • Innervated by Hering’s nerve, a branch of CN IX
        • Goes to nucleus solitarius in medulla
    • Nerve Entry/Exit
      • Exits brainstem from postolivary sulcus in medulla
        • Taste, visceral afferents to the solitary nucleus in medulla
        • Motor output from nucleus ambiguus in medulla
        • Parasympathetics from inferior salivatory nucleus in pons
        • Sensation to spinal trigeminal nucleus in medulla
    • Cranial foramen
      • Jugular foramen
    • Reflexes
      • Gag reflex (afferent sensory)