Glossopharyngeal Nerve (CN IX)
The glossopharyngeal nerve is the ninth cranial nerve serving the tongue (glossal) and pharynx. It provides sensation from the posterior tongue and pharynx, taste from the posterior tongue, and carries vital information from the carotid body and sinus for blood pressure and oxygen regulation.
Origin
Motor: nucleus ambiguus; Sensory: superior and inferior (petrosal) ganglia; Parasympathetic: inferior salivatory nucleus
Foramina
Jugular foramen
Course
Exits lateral medulla → jugular foramen → descends between internal jugular vein and internal carotid → branches to pharynx, tongue, carotid body/sinus
Functions
- •Taste from posterior 1/3 of tongue
- •Sensation from posterior tongue, tonsils, pharynx, middle ear
- •Carotid body chemoreception (O2, CO2, pH)
- •Carotid sinus baroreception (blood pressure)
- •Motor to stylopharyngeus
- •Parotid gland secretion
- •Afferent limb of gag reflex
Branches
Structures Innervated
- →Posterior 1/3 tongue (taste and sensation)
- →Oropharynx
- →Tonsils
- →Eustachian tube
- →Middle ear
- →Stylopharyngeus muscle
- →Parotid gland (parasympathetic)
Clinical Testing
Test gag reflex (IX afferent, X efferent). Test taste on posterior tongue (bitter). Check sensation in posterior pharynx. Difficult to isolate CN IX from X clinically.
Clinical Relevance
Glossopharyngeal neuralgia causes severe pain in throat, tongue, and ear triggered by swallowing. Isolated CN IX palsy is rare; usually part of jugular foramen syndrome (IX, X, XI). The gag reflex tests CN IX (afferent) and X (efferent).
Study Tips
- ✓CN IX = posterior 1/3 tongue; CN VII = anterior 2/3 tongue (taste)
- ✓Stylopharyngeus is the only muscle innervated by CN IX
- ✓Gag reflex: IX in, X out (afferent/efferent)
- ✓Jugular foramen: CN IX, X, XI exit together
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Common questions about this cranial nerve
CN IX carries afferent signals from the carotid sinus (baroreceptors detecting pressure) and carotid body (chemoreceptors detecting O2, CO2, pH). This information reaches the medulla to regulate heart rate, blood pressure, and respiration.
The glossopharyngeal nerve innervates the pharynx and posterior tongue. Swallowing, talking, or chewing stimulates these areas, triggering paroxysms of severe pain in the throat, tongue base, and ear in affected patients.
Touch the posterior pharyngeal wall with a tongue depressor. The afferent limb is CN IX (sensation), and the efferent limb is CN X (motor to pharynx). Absent reflex suggests CN IX or X lesion; requires bilateral assessment.