Sensory Nerve supply of Anterior 2/3rd tongue
**Core Concept**
The anterior 2/3rd of the tongue receives its sensory nerve supply from the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3). This nerve is responsible for transmitting taste, temperature, and touch sensations from the anterior two-thirds of the tongue.
**Why the Correct Answer is Right**
The lingual nerve arises from the anterior trunk of the mandibular nerve, which is formed by the fusion of the nerve's three branches: the anterior, middle, and posterior trunks. The lingual nerve then divides into the chorda tympani, the lingual nerve proper, and the submandibular ganglion. The lingual nerve proper is responsible for transmitting sensory information from the anterior two-thirds of the tongue. The chorda tympani carries taste fibers from the anterior two-thirds of the tongue to the facial nerve.
**Why Each Wrong Option is Incorrect**
***Option A:** This option is incorrect because the hypoglossal nerve (CN XII) primarily supplies motor innervation to the tongue, not sensory innervation.
***Option B:** This option is incorrect because the glossopharyngeal nerve (CN IX) supplies the posterior one-third of the tongue, not the anterior two-thirds.
***Option C:** This option is incorrect because the vagus nerve (CN X) supplies the pharynx and larynx, but not the tongue.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the lingual nerve is at risk during surgical procedures involving the mandible, such as third molar extractions, which can lead to nerve damage and altered sensation in the anterior two-thirds of the tongue.
**Correct Answer:** B. Glossopharyngeal nerve