M01.02.026 Mandibular Nerve

The mandibular nerve is a terminal branch of the trigeminal nerve (CN V), alongside the maxillary and ophthalmic nerves. It serves both sensory and motor roles, distinguishing it from the other branches of the trigeminal nerve.

Overview of the Mandibular Nerve

• Classification: Mixed nerve (sensory and motor).
• Functions: Sensory innervation of the face and oral structures; motor innervation of muscles of mastication.
• Associated Parasympathetic Fibers: Carries autonomic fibers from other cranial nerves.

Anatomical Course

The mandibular nerve arises from:

• Sensory nuclei: Mesencephalic, principal sensory, and spinal nuclei of the trigeminal nerve.
• Motor nucleus: Trigeminal motor nucleus.

Pathway

1. Origin: The sensory and motor roots emerge from the brainstem.
2. Exit: Leaves the cranium through the foramen ovale.
3. Infratemporal Fossa: Divides into its branches.

Branches and Their Functions

Auriculotemporal Nerve

• Roots:
  • Superior root: Sensory fibers.
  • Inferior root: Secretory-motor parasympathetic fibers (from CN IX) to the parotid gland.
• Innervation:
  • Anterior auricle.
  • Lateral temple.
  • External acoustic meatus.
  • Tympanic membrane.

Buccal Nerve

• Type: Sensory.
• Pathway: Passes between the two heads of the lateral pterygoid muscle.
• Innervation: Buccal membranes and second and third molar teeth.

Inferior Alveolar Nerve

• Type: Mixed (sensory and motor).
• Motor Component: Gives rise to the mylohyoid nerve, innervating:
  • Mylohyoid muscle.
  • Anterior belly of the digastric muscle.
• Sensory Component:
  • Travels through the mandibular canal.
  • Emerges as the mental nerve, innervating:
    • Chin.
    • Lower lip.

Lingual Nerve

• Type: Sensory and autonomic.
• Functions:
  • General sensory: Anterior two-thirds of the tongue.
  • Special sensory (taste): Via chorda tympani (CN VII).
  • Parasympathetic fibers: Innervate submandibular and sublingual glands.

Functions of the Mandibular Nerve

Sensory Functions

• Skin of the lower face, chin, and lower lip.
• Inferior row of teeth and gingiva.
• Anterior two-thirds of the tongue (general sensation).

Motor Functions

The mandibular nerve innervates:

1. Muscles of mastication:
   • Masseter.
   • Temporalis.
   • Medial and lateral pterygoids.
2. Other muscles:
   • Tensor tympani: Stabilizes malleus, dampening sounds.
   • Tensor veli palatini: Elevates the soft palate.
   • Mylohyoid: Elevates the hyoid bone.
   • Anterior belly of the digastric: Aids in swallowing.

Autonomic Functions

• Submandibular and Sublingual Glands: Parasympathetic fibers via chorda tympani (CN VII).
• Parotid Gland: Parasympathetic fibers via auriculotemporal nerve (CN IX).

Clinical Relevance

Mandibular Nerve Blocks

• Used in dental surgeries to provide anesthesia.
• Mandibular Nerve Block:
  • Affects the entire mandibular nerve distribution.
  • Targets the region near the second molar tooth.
• Inferior Alveolar Nerve Block:
  • Provides anesthesia for the inferior teeth.
  • Spares the rest of the mandibular nerve’s distribution.

Points to Remember

• The mandibular nerve is the only branch of CN V with motor fibers.
• It carries parasympathetic fibers from CN VII and CN IX.
• Auriculotemporal, buccal, inferior alveolar, and lingual nerves are its major branches.
• Clinical importance in nerve blocks for dental and surgical procedures.

Table: Summary of Mandibular Nerve Functions

References

1. TeachMeSeries Ltd (2024). Anatomy of the Mandibular Nerve. TeachMe Anatomy.