Nerve supplying posterior one third of the tongue, oropharynx and soft palate is:

  # Nerve supplying posterior one third of the tongue, oropharynx and soft palate is:

A. Lingual nerve

B. Glossopharyngeal nerve

C. Chorda tympani nerve

D. Vagus nerve

The correct answer is B. Glossopharyngeal nerve.

Explanation

The Glossopharyngeal nerve (CN IX) is the primary sensory nerve for the posterior one-third of the tongue, the oropharynx, and the tonsillar region.

• Posterior 1/3 of the Tongue: CN IX provides both general sensation (pain, touch, temperature) and special sensation (taste) to this region (via the lingual branches).

• Oropharynx: CN IX supplies the mucosa of the oropharynx, the palatine tonsils, and the faucial pillars. It acts as the afferent limb of the gag reflex.

• Soft Palate: While the sensory supply to the soft palate is complex (involving the lesser palatine nerves from CN V2), the glossopharyngeal nerve contributes to the sensory innervation of the soft palate via the pharyngeal plexus.

Why the other options are incorrect:

• Lingual nerve: A branch of the Mandibular nerve (CN V3). It supplies general sensation (touch, pain, temperature) only to the anterior two-thirds of the tongue.

• Chorda tympani nerve: A branch of the Facial nerve (CN VII). It carries taste sensation from the anterior two-thirds of the tongue (hitchhiking with the Lingual nerve).

• Vagus nerve: Supplies sensation to the area even more posterior than the posterior third—specifically the epiglottis and the extreme root of the tongue (valleculae). It provides motor supply to the muscles of the soft palate (except the Tensor Veli Palatini), but it is not the primary sensory nerve for the posterior third of the tongue.