Which of the following statements about the trigeminal nerve is CORRECT?

Explanation

## Trigeminal Nerve — Structural Overview **Key Point:** The trigeminal nerve (CN V) is a mixed nerve with both sensory and motor components. The mandibular division (V3) is the **only** division that carries motor fibers (to muscles of mastication and four tensor muscles) and is also the division through which parasympathetic fibers hitchhike to reach target glands. ### Why Option B is Correct The mandibular division (V3) is unique among the three trigeminal divisions in that: 1. It carries **motor fibers** from the trigeminal motor nucleus to the muscles of mastication (masseter, temporalis, medial and lateral pterygoids), mylohyoid, anterior belly of digastric, tensor veli palatini, and tensor tympani. 2. Parasympathetic fibers from CN IX (glossopharyngeal) travel via the lesser petrosal nerve to the **otic ganglion**, which is closely associated with V3, and post-ganglionic fibers then hitchhike with the auriculotemporal branch of V3 to supply the parotid gland. Similarly, parasympathetic fibers from CN VII travel via the chorda tympani to join the lingual nerve (a branch of V3) to reach the submandibular ganglion, supplying the submandibular and sublingual glands. Thus, V3 is the only division associated with parasympathetic fiber transmission, making Option B correct. ### Why the Other Options Are Wrong | Division | Origin | Sensory Supply | Motor Supply | | --- | --- | --- | --- | | **Ophthalmic (V1)** | Trigeminal ganglion | Forehead, upper eyelid, cornea, nose, meninges | None (purely sensory) | | **Maxillary (V2)** | Trigeminal ganglion | Upper face, upper teeth, palate, nasal cavity | None (purely sensory) | | **Mandibular (V3)** | Trigeminal ganglion | Lower face, lower teeth, anterior 2/3 tongue, meninges | Muscles of mastication, mylohyoid, anterior belly of digastric, tensor veli palatini, tensor tympani | - **Option A** is incorrect: The trigeminal ganglion (Gasserian/semilunar ganglion) is located in **Meckel's cave (trigeminal cave)** in the middle cranial fossa at the apex of the petrous temporal bone — NOT in the cavernous sinus (which is nearby but anatomically distinct). - **Option C** is incorrect: The trigeminal nerve is a **mixed nerve** — it carries both sensory and motor fibers. The motor root exits with V3. - **Option D** is incorrect: V1 (ophthalmic division) is **purely sensory**; motor innervation to the muscles of mastication is carried by V3. **High-Yield:** Only V3 carries motor fibers. V1 and V2 are purely sensory. Parasympathetic fibers hitchhike with V3 (otic ganglion → parotid via auriculotemporal nerve) and with V2 (pterygopalatine ganglion → lacrimal/nasal glands), but these originate from CN IX and CN VII respectively, not from the trigeminal nerve itself. **Clinical Pearl:** Damage to V3 can cause weakness of mastication (jaw deviates toward the side of the lesion on opening), loss of sensation over the lower face, and loss of the jaw-jerk reflex. (Gray's Anatomy, 41st ed.; Snell's Clinical Neuroanatomy, 8th ed.)