## **Core Concept**
The masseter muscle is one of the muscles of mastication. The muscles of mastication are primarily supplied by the **mandibular division of the trigeminal nerve (V3)**, which is responsible for controlling the muscles involved in chewing.

## **Why the Correct Answer is Right**
The masseter muscle, involved in elevating the mandible to close the jaw, is innervated by the **masseteric nerve**. This nerve is a branch of the **anterior division of the mandibular nerve (V3)**, which itself is a division of the trigeminal nerve. The masseteric nerve provides the necessary motor innervation for the masseter muscle to function.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The **facial nerve (cranial nerve VII)** primarily controls muscles of facial expression and taste to the anterior two-thirds of the tongue, among other functions. It does not supply the muscles of mastication.
* **Option B:** The **median nerve** is a major nerve of the upper limb, responsible for innervating muscles of the anterior forearm and thenar eminence, as well as providing sensation to the palmar surface of the thumb, index, and middle fingers. It has no role in the innervation of the muscles of mastication.
* **Option C:** While not listed, if another option were a nerve not directly associated with the trigeminal nerve or specifically with mastication, it would be incorrect for similar reasons related to its function and innervation territory.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that all muscles of mastication (masseter, temporalis, medial pterygoid, and lateral pterygoid) are innervated by branches of the **mandibular division of the trigeminal nerve (V3)**. This is crucial for understanding both the motor function of the trigeminal nerve and for clinical procedures or assessments involving the jaw and facial muscles.

## **Correct Answer:** D.