The posterior 1/3 of the tongue is supplied by….nerve
**Core Concept**
The posterior 1/3 of the tongue is supplied by a branch of the glossopharyngeal nerve, which is responsible for sensory innervation of this region. This is part of the complex innervation of the tongue, which is crucial for taste, swallowing, and speech.
**Why the Correct Answer is Right**
The glossopharyngeal nerve (cranial nerve IX) provides sensory innervation to the posterior 1/3 of the tongue, including the taste sensation from the circumvallate papillae. This is mediated by the lingual branch of the glossopharyngeal nerve, which contains sensory fibers that transmit information to the brain. The lingual nerve, a branch of the mandibular division of the trigeminal nerve, supplies the anterior 2/3 of the tongue.
**Why Each Wrong Option is Incorrect**
**Option A:** The vagus nerve (cranial nerve X) supplies the epiglottis and the larynx, but not the posterior 1/3 of the tongue.
**Option B:** The facial nerve (cranial nerve VII) is responsible for taste sensation from the anterior 2/3 of the tongue, not the posterior 1/3.
**Option C:** The trigeminal nerve (cranial nerve V) supplies the face and the anterior 2/3 of the tongue, but not the posterior 1/3.
**Clinical Pearl / High-Yield Fact**
The glossopharyngeal nerve also supplies the stylopharyngeus muscle, which is involved in swallowing and is a key landmark for the location of the glossopharyngeal nerve.
**Correct Answer:** C. Glossopharyngeal nerve