Overview and Origin of Mandibular Nerve
General Character
- Mandibular nerve (V3) is the largest of the three divisions of the trigeminal nerve (CN V)
- It is the only division with a motor root — it carries both sensory and motor fibres
- Classified as a mixed nerve (sensory + motor)
Roots
| Root | Origin | Character |
|---|---|---|
| Large sensory root | From lateral part of trigeminal (semilunar/Gasserian) ganglion | General somatic afferent |
| Small motor root | Bypasses the ganglion, runs medial to sensory root | Special visceral efferent |
- Both roots exit the skull through foramen ovale in the greater wing of sphenoid
- They unite just below the foramen ovale in the infratemporal fossa to form the main trunk
Main Trunk (Undivided Segment)
The two roots unite to form a short undivided trunk (~2–3 mm) which immediately gives off:
| Branch | Type | Distribution |
|---|---|---|
| Meningeal branch (nervus spinosus) | Sensory | Re-enters skull through foramen spinosum with middle meningeal artery; supplies dura mater of middle cranial fossa and mastoid air cells |
| Nerve to medial pterygoid | Motor | Supplies medial pterygoid; also gives branches to tensor tympani and tensor veli palatini |
Division
The main trunk then divides into:
| Division | Character | Branches |
|---|---|---|
| Anterior division (smaller) | Predominantly motor | 3 motor + 1 sensory (buccal) |
| Posterior division (larger) | Predominantly sensory | 3 sensory branches + motor to mylohyoid |
Mnemonic (Trigeminal branches): “O My Mamma” — Ophthalmic (V1), Maxillary (V2), Mandibular (V3)
Relations at Foramen Ovale
The nerve lies in the infratemporal fossa, medial to the lateral pterygoid, lateral to the tensor veli palatini, with the otic ganglion suspended from its medial aspect.