**Question:** In fracture maxilla, most common nerve involved is

A. Ophthalmic nerve (V1)
B. Inferior alveolar nerve (V3)
C. Nasal branch of maxillary nerve (V2)
D. Trigeminal nerve (V)

**Correct Answer:** D. Trigeminal nerve (V)

**Core Concept:**
The trigeminal nerve (Cranial nerve V) is a mixed somatic and autonomic nerve that plays a crucial role in the innervation of the head and face, including the maxilla. It has three branches:

1. Ophthalmic branch (V1): Supplies the eye, forehead, and upper eyelid.
2. Maxillary branch (V2): Innervates the maxilla, nose, and upper lip.
3. Mandibular branch (V3): Supplies the lower jaw, chin, and lower lip.

**Why the Correct Answer is Right:**
In a fracture of the maxilla, the most commonly affected branch is the maxillary branch (V2) as it supplies the maxilla, a region that is frequently involved in maxillary fractures.

**Why Each Wrong Option is Incorrect:**
A. Ophthalmic nerve (V1) is less commonly involved in maxillary fractures due to its relatively superficial course and protection by the orbit.
B. The inferior alveolar nerve (V3) is less involved because it supplies the lower jaw, chin, and lower lip, which are less prone to fractures compared to the maxilla.
C. The nasal branch of the maxillary nerve (V2) is also less commonly affected due to its protection within the nasal cavity.

**Clinical Pearl:**
Understanding the anatomy and embryology of the trigeminal nerve is essential for understanding the potential nerve injuries in maxillary fractures, as well as for making accurate diagnoses and planning appropriate surgical interventions.