The 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 back to the brain from a peripheral area. The third division of the trigeminal nerve is the mandibular nerve. This division innervates the lower third of the face which includes the lower lip, the jaw, the preauricular area and the temporal area.
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 gasseri ganglion.
- The pontine region also gives proprioceptive fibers to the nerve bundle before it reaches the gasseri 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 nerve, 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 otic ganglion gives branches to the following nerves: the nerve of the tenor palatini muscle and the mylohyoid nerve, which innervates the mylohyoid muscle.
- The second group nerves that innervate muscles are also motoric and aid swallowing.
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 third facial area that is innervated by the third division of the trigeminal nerve and consists of the lower lip, the jaw, the preauricular area and a larger portion of the temporal Area.
- 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.
- 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 post ganglionic 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 gasseri ganglion (ganglion of the trigeminal nerve).
- The terminal synapses are on the pontine nucleus and the spinal nucleus and tract.
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