Trigeminal Nerve: Mandibular Branch (V3)

Overview

• The trigeminal nerve is the largest cranial nerve and is also the 5th cranial nerve.
• Knowledge of the trigeminal nerve is important for dental professionals.
• It has three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3).

Mandibular Branch (V3)

• The mandibular branch (V3) is the largest of the three divisions of the trigeminal nerve.
• It exits the skull through the foramen ovale.
• The mandibular branch contains both sensory and motor fibers.

Sensory Supply

• The mandibular branch supplies the mandibular teeth and supporting structures.
• It also supplies the mucosa of the anterior two-thirds of the tongue and the floor of the mouth.
• The skin of the lower face, parts of the temporal region, and the outer ear receive sensory innervation from the mandibular branch.

Motor Supply

• Muscles of mastication are innervated by the mandibular branch.
• It also innervates the mylohyoid muscle, the anterior belly of the digastric muscle, tensor veli palatini, and tensor tympani.

Anatomical Course

• Shortly after exiting the skull, the mandibular nerve divides into a small anterior trunk and a larger posterior trunk.
• Branches originate directly from the main nerve before it divides, including the meningeal branch and the nerve to the medial pterygoid muscle.

Anterior Trunk Branches

• The masseteric nerve is a branch of the anterior trunk.
• The deep temporal nerves arise from the anterior trunk.
• The nerve to the lateral pterygoid muscle originates from the anterior trunk.
• The long buccal nerve is a branch of the anterior trunk.

Posterior Trunk Branches

• The auriculotemporal nerve is a branch of the posterior trunk.
• The lingual nerve originates from the posterior trunk.
• The inferior alveolar nerve is a branch of the posterior trunk.

Medial Pterygoid Nerve

• The medial pterygoid nerve is a motor branch, which enters the deep surface of the medial pterygoid muscle.
• It also supplies the tensor tympani and tensor veli palatini muscles.
• Its action is to elevate the jaw.

Masseter

• The masseteric nerve, the first branch of the anterior trunk, innervates the masseter.
• The masseteric nerve crosses the masseter muscle between the coronoid process and the condyle of the mandible.
• It provides an articular branch to the temporomandibular joint (TMJ).
• The masseter muscle elevates the mandible, closing the mouth.

Temporalis

• The temporalis muscle is innervated by anterior and deep temporal nerves.
• The temporalis muscle elevates the mandible, closing the mouth.

Lateral Pterygoid

• The nerve to the lateral pterygoid muscle may run partly with the long buccal nerve.
• The lateral pterygoid muscle depresses the mandible, opening the mouth.

Long Buccal Nerve

• The long buccal nerve is the only sensory branch of the anterior trunk.
• It emerges between the heads of the lateral pterygoid muscle.
• It runs on the lateral surface of the buccinator muscle in the cheek, near the retromolar fossa of the mandible.
• This nerve gives branches to the skin of the cheek.
• The long buccal nerve pierces the buccinator muscle to supply the buccal sulcus and buccal gingivae of the mandibular molars and premolars.

Auriculotemporal Nerve

• The auriculotemporal nerve is the first branch of the posterior trunk and is sensory.
• It provides autonomic innervation to the parotid gland via fibers from the otic ganglion.
• Two roots unite and run backward under the lateral pterygoid muscle, lying between the condyle and the sphenomandibular ligament.
• The auriculotemporal nerve emerges between the TMJ and the external auditory meatus.
• It ascends on the side of the head.

Lingual Nerve

• The lingual nerve is the second branch of the posterior trunk and is primarily sensory.
• It unites with the chorda tympani branch of the facial nerve, receiving parasympathetic fibers for the submandibular and sublingual glands.
• It emerges from under the lateral pterygoid muscle.
• The lingual nerve curves downwards and forwards between the ramus of the mandible and the medial pterygoid muscle, i.e., the pterygomandibular space.
• It lies anterior to but deeper than the inferior alveolar nerve.
• The lingual nerve then passes towards the floor of the mouth.

Lingual Nerve Supply

• The lingual nerve twists around the submandibular duct of the salvary gland.
• It enters the tongue behind the sublingual salivary gland.
• The lingual nerve supplies the mucosa covering the anterior two-thirds of the dorsum of the tongue.
• It also supplies the under surface of the tongue, the floor of the mouth, and the lingual gingivae of the mandibular teeth.

Inferior Alveolar (Dental) Nerve

• The inferior alveolar nerve has both sensory and motor functions.
• It descends deep to the lateral pterygoid muscle behind the lingual nerve.
• The inferior alveolar nerve enters the mandibular foramen.
• It travels in the inferior dental or mandibular canal in the mandible.
• Near the premolars, it divides into the mental nerve and the incisive nerve.
• The mental nerve emerges at the mental foramen.
• The incisive nerve runs anteriorly in the incisive canal.

Mylohyoid Nerve

• The mylohyoid nerve (a branch of the inferior alveolar) is given off just before the mandibular foramen.
• It runs in the mylohyoid groove to supply the mylohyoid muscle and the anterior belly of the digastric muscle (motor).
• It depresses the mandible (when the hyoid is fixed) or elevates the hyoid (when the mandible is fixed) during swallowing.

Inferior Alveolar Nerve - Specific Branches

• The inferior alveolar nerve supplies the mandibular molars, premolars, and their supporting structures, including the gingivae.
• The mental nerve supplies the skin of the chin, lower lip, and labial gingivae of the anterior mandibular teeth.
• The incisive nerve innervates the mandibular incisors and canines.