Which cranial nerve is responsible for innervation of the muscles of mastication?

Explanation

## Trigeminal Nerve (CN V) — Motor Division **Key Point:** The trigeminal nerve (CN V) is the only cranial nerve that innervates the muscles of mastication. ### Muscles of Mastication Innervated by CN V~3~ The motor division of the mandibular division (CN V~3~) supplies: 1. Masseter 2. Temporalis 3. Medial pterygoid 4. Lateral pterygoid **High-Yield:** CN V~3~ also innervates the tensor veli palatini, tensor tympani, mylohyoid, anterior belly of the digastric, and the lingual nerve (sensory to anterior 2/3 tongue). ### Why CN V and Not Others? | Cranial Nerve | Motor Function | Muscles Innervated | | --- | --- | --- | | **CN V (Trigeminal)** | Mastication | Masseter, temporalis, medial/lateral pterygoid | | CN VII (Facial) | Facial expression | Orbicularis oculi, orbicularis oris, buccinator | | CN IX (Glossopharyngeal) | Pharyngeal | Stylopharyngeus | | CN X (Vagus) | Pharyngeal/laryngeal | Pharyngeal constrictors, intrinsic laryngeal muscles | **Clinical Pearl:** Damage to CN V~3~ results in inability to clench the jaw and deviation of the jaw toward the affected side due to unopposed action of the lateral pterygoid on the contralateral side. **Mnemonic:** **"V chews"** — The Trigeminal (V) nerve controls chewing (mastication).