**Question:** All of the following are innervated by trigeminal nerve except

A. Masticatory muscles
B. Nasal mucosa
C. Corneal surface of the eye
D. Trachea

**Core Concept:**
The trigeminal nerve is a cranial nerve that plays a crucial role in sensory innervation, motor control, and autonomic functions. It is responsible for sensory innervation of the face, including the skin, muscles, and mucous membranes. The trigeminal nerve consists of three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3).

**Why the Correct Answer is Right:**
The correct answer is D. Trachea, as it is not innervated by the trigeminal nerve. Instead, the trachea receives its innervation from the vagus nerve (C1-C12), specifically the vagal (C1-C4) and pharyngeal branches (C5-C6). The vagus nerve is a mixed nerve that contains both sensory and motor fibers, whereas the trigeminal nerve is a purely sensory nerve.

**Why Each Wrong Option is Incorrect:**
A. Masticatory muscles (Option A) are innervated by the masseteric and temporalis muscles, which are branches of the trigeminal nerve (V3). This option is incorrect because it refers to muscles innervated by the trigeminal nerve.
B. Nasal mucosa (Option B) is innervated by the ophthalmic division of the trigeminal nerve (V1). This option is incorrect because it refers to a specific part of the trigeminal nerve being innervated.
C. Corneal surface of the eye (Option C) is innervated by the ophthalmic division of the trigeminal nerve (V1), but the corneal surface of the eye also receives parasympathetic innervation from the oculomotor nerve (CN III), specifically the ciliary ganglion and the long ciliary nerves. This option is incorrect because it mentions another nerve contributing to corneal innervation.

**Clinical Pearl:**
The corneal innervation is a result of the combined action of the ophthalmic division of the trigeminal nerve (V1) and the oculomotor nerve (CN III). Understanding these innervation patterns is essential for understanding various clinical conditions involving the cornea, such as corneal hypoesthesia (insensitivity) and neuropathic oculomotor nerve disorders.

**Correct Answer:** C. Corneal surface of the eye (Option C) is innervated by the ophthalmic division of the trigeminal nerve (V1), which supplies the skin, glands, and mucous membranes of the face. This option is correct because it specifically mentions the trigeminal nerve as the source of corneal innervation.