Sensory supply to tonsil is by which nerve?
**Core Concept**
The sensory supply to the tonsils is provided by the glossopharyngeal nerve, which is responsible for transmitting sensory information from the posterior one-third of the tongue, the tonsils, and the soft palate to the brain.
**Why the Correct Answer is Right**
The glossopharyngeal nerve (cranial nerve IX) is a mixed nerve that carries both sensory and motor fibers. The sensory fibers of the glossopharyngeal nerve supply the posterior one-third of the tongue, the tonsils, and the soft palate, providing sensation to these areas. This includes pain, temperature, and touch. The glossopharyngeal nerve also provides secretory fibers to the parotid gland.
**Why Each Wrong Option is Incorrect**
**Option A:** The vagus nerve (cranial nerve X) primarily supplies the larynx, trachea, and esophagus, and is not responsible for the sensory supply to the tonsils.
**Option B:** The facial nerve (cranial nerve VII) primarily supplies the muscles of facial expression, taste to the anterior two-thirds of the tongue, and some motor functions to the stapedius and stylohyoid muscles.
**Option C:** The trigeminal nerve (cranial nerve V) is responsible for sensory supply to the face, including the skin of the face, the nasal cavity, and the oral cavity, but not the tonsils.
**Clinical Pearl / High-Yield Fact**
The glossopharyngeal nerve is also responsible for the gag reflex, which is an important clinical sign in assessing the integrity of the nervous system.
**Correct Answer:** C. Glossopharyngeal nerve.