Mandibular branch of the trigeminal nerve
The trigeminal nerve is the fifth of the twelve Cranial Nerves. It consists of both afferent and efferent motoric and sensory fibers as well as proprioceptive, sympathetic and parasympathetic fibers that are divided into three main branches: the ophthalmic nerve, the maxillary nerve, and the mandibular nerve.
Together these branches innervate the three areas of the head. The word afferent means toward the centre, as in from a peripheral area of a limb to the central nervous system. The word efferent is the opposite of afferent, meaning away from the centre and toward the periphery; when the stimulus is carried to the peripheral area from the brain.
The third division of the trigeminal nerve is the mandibular nerve. This division carries sensory information from the lower third of the face which includes the lower lip, the jaw, the preauricular area, the temporal area and the meninges of the anterior and middle cranial fossa. Also, it is responsible for the motor innervation of the muscles of mastication, the mylohyoid, tensor tympani, tensor veli palatini muscles and the anterior belly of the digastric muscle.
To remember the muscles innervated by the motor fibers of the mandibular nerve, you can use the following mnemonic: "My Anus Temporarily Meets the Toilet", which stands for;
- Anterior belly of the digastric muscle
- Tensor veli palatini
- Masticatory muscles
- Tensor tympani
Pathway and branches
The pathway for the efferent fibers of the main branch of the trigeminal nerve before and after its division is the following (From the initiation in the brain to the termination in the periphery):
- The motor nucleus of the trigeminal nerve gives efferent fibers to the trigeminal ganglion, otherwise known as the semilunar Gasserian ganglion.
- The pontine region also gives proprioceptive fibers to the nerve bundle before it reaches the Gasserian ganglion.
- From there the fibers continue in the mandibular branch of the trigeminal nerve or the third division.
- At the level of the mandibular tubercle, the nerve gives the following branches: the deep temporal nerves (anterior & posterior), the nerve of the lateral pterygoid muscle and the masseteric nerve, the nerve of the tensor veli palatine muscle and nerve of the medial pterygoid muscle.
- These nerves innervate their corresponding muscles motorically and aid in speech and mastication.
- Other fibers that didn’t branch off synapse on the otic ganglion which is at the same level.
The pathway for afferent sensory fibers of the mandibular nerve from the proprioceptors until the trigeminal nuclei (after the merger into one main cranial nerve) is the following (from the initiation in the periphery to the termination in the brain):
- The mandibular nerve divides into two main nerve bundles at the level of the mandibular tubercle and also gives off an additional branch: the buccal nerve (not to be confused with the nerve innervating the buccinator muscle).
- The first main branch is the inferior alveolar nerve which branches into the inferior dental plexus and the mental nerve and innervates the mandibular teeth and gums with sensory fibers.
- The second branch is the lingual nerve, which innervates the tongue, the floor of the mouth and the submandibular glands and sublingual glands with sensory fibers from the trigeminal nerve and parasympathetic fibers from the chorda tympanii of the facial nerve (CN VII).
- The branches of the lingual nerve either go straight into the tongue with where they control taste in the anterior two-thirds of the tongue or they synapse in the submandibular ganglion as parasympathetic fibers and the postganglionic fibers innervate the salivary glands.
- The two main branches of the mandibular nerve synapse on the otic ganglion.
- The mandibular nerve continues on and synapses on the Gasserian ganglion (ganglion of the trigeminal nerve).
- The terminal synapses are in the pontine nucleus and the spinal nucleus and tract.
- The mandibular nerve is the third and largest division of the trigeminal nerve.
- It has both sensory and motor function.
- It exists the skull through the foramen ovale.
- It carries sensory information from the buccal area (buccal nerve), anterior two-thirds of the tongue (lingual nerve), temporal region (deep temporal nerves). Also, it carries motor innervation to the mastication muscles (masseter, pterygoids, temporalis), mylohyoid and anterior belly of the digastric.