Mandibular nerve (CN V3)
The mandibular nerve (third division of fifth cranial nerve, third division of trigeminal nerve, mandibular division of trigeminal nerve, CN V3, latin: nervus mandibularis) is the third branch of the trigeminal nerve, a mixed nerve consisting of general somatic efferent (motor) and general somatic afferent (sensory) fibers. The sensory fibers of the mandibular nerve innervate several skin regions of the face, as well as mucosa of the oral cavity, the lower teeth and gingiva. The motor branches of the mandibular nerve supply muscles of the first branchial arch, including all of the muscles of mastication.
The mandibular nerve emerges from the lateral part of the trigeminal ganglion and exits the middle cranial fossa via the foramen ovale. The mandibular division of the trigeminal nerve is a large, mixed nerve.
The mandibular nerve carries general somatic afferent fibers that provide sensory innervation for the skin of the temporal region of the scalp, skin of the external meatus, the tympanic membrane, the lower part of the face. The sensory fibers of the mandibular nerve also supply the mucosa of the floor of the oral cavity, the anterior two thirds of the tongue, and the teeth and gums of the lower jaw (mandible).
The motor branches of the mandibular nerve carrying general somatic efferent fibers supply all of the muscles that developed from the first branchial arch, which are:
- masseter muscle,
- medial pterygoid muscle,
- lateral pterygoid muscle,
- temporal muscle,
- tensor tympani muscle,
- tensor veli palatini muscle,
- mylohyoid muscle,
- anterior belly of digastric muscle.
The sensory root of the mandibular nerve emerges from the lateral part of the trigeminal ganglion, while the smaller motor root passes below the trigeminal ganglion. Both of the roots exit the cranial cavity through the foramen ovale and reach the infratemporal fossa, and both unite just outside of the skull. Then the mandibular nerve passes between the tensor veli palatini and lateral pterygoid muscles, and gives off a meningeal branch and the medial pterygoid muscle supplying motor innervation to the medial pterygoid, and on its way - to the tensor tympani, and tensor veli palatini muscles as well. The mandibular nerve then divides into into a small anterior and larger posterior trunk. The anterior portion of the nerve gives off motor branches to the four muscles of mastication and a sensory branch to the cheek, the buccal nerve. The posterior trunk of the mandibular nerve gives off motor fibers to supply the mylohyoid muscle and the anterior belly of the digastric muscle, and three main sensory branches: the auriculotemporal, lingual, and inferior alveolar nerves.
Thus, the main branches arising from the mandibular nerve are:
- medial pterygoid nerve (motor),
- lateral pterygoid nerve (motor),
- masseteric nerve (motor),
- deep temporal nerve (motor),
- meningeal branch (sensory),
- buccal nerve (sensory),
- auriculotemporal nerve (sensory),
- lingual nerve (sensory),
- inferior alveolar nerve (motor and sensory).
The medial pterygoid nerve is a motor branch that arises from the mandibular nerve in the infratemporal fossa before the mandibular nerve divides into two portions. The medial pterygoid nerve travels through the otic ganglion (without synapsing) to innervate the medial pterygoid muscle, supplying tensor veli palatini and tensor tympani muscles with branches along the way.
The lateral pterygoid nerve arises from the mandibular nerve in the infratemporal fossa lower than the medial pterygoid nerve and carries motor fibers. It is a short nerve which perforates the lateral pterygoid muscle and innervates it.
The masseteric nerve is one of the motor branches of the mandibular nerve. The masseteric nerve arises in the infratemporal fossa, runs above the mandibular notch and penetrates the masseter muscle from inside, innervating it.
The deep temporal nerve is a motor branch of the mandibular nerve, which arises in the infratemporal fossa, runs laterally above the infratemporal crest, then upward to the temporal fossa and reaches the temporalis muscle innervating it.
The meningeal branch of the mandibular nerve arises in the infratemporal fossa and returns to the cranial cavity via the foramen spinosum. The meningeal branch carries sensory fibers to innervate the dura mater in the posterior region of the middle cranial fossa.
The buccal nerve is a sensory branch of the mandibular nerve, which passes through the buccinator muscle and transmits sensory information from the skin covering the buccinator muscle, as well from the mucosa of the cheek, and from the second and third molar teeth. The buccal nerve passes between the heads of the lateral pterygoid muscle, courses through the anterior surface of the masseter muscle, and runs with the buccal branches of the facial nerve (CN VII).
The auriculotemporal nerve is a sensory nerve that originates from the posterior part of the mandibular nerve. The auriculotemporal nerve emerges onto the face at the back of the temporomandibular joint. Before it gives off parotid branches, the auriculotemporal nerve unites with the lesser petrosal nerve, which carries postganglionic fibers from the otic ganglion. Thereby the parotid branches of the auriculotemporal nerve provide secretomotor innervation to the parotid gland. After that, the auriculotemporal nerve ascends and runs behind the superficial temporal vessels, crosses over the posterior root of the zygomatic process of the temporal bone, where it divides into superficial temporal branches, and innervates the skin in the temporal region, the auricle, external acoustic meatus, and outer side of the tympanic membrane.
The lingual nerve is a sensory nerve which derives from the mandibular nerve, passes to the tongue where it distributes branches from the terminal sulcus up to the apex providing transmission of general sensation (touch, pain, temperature, but not taste) from the mucosa of the tongue and from the filiform papillae.
The inferior alveolar nerve is a mixed branch of the mandibular nerve, which runs through the mandibular foramen into the mandibular canal, but before entering the canal it gives off the mylohyoid nerve carrying motor fibers to innervate both the mylohyoid muscle and the anterior belly of the digastric muscle. In the mandibular canal the sensory fibers of the inferior alveolar nerve form the inferior dental plexus. The nerve terminates as the mental nerve emerging on the chin. The mental nerve emerges on the face through the mental foramen to supply the skin of the chin, the lower lip and the gingiva of the inferior jaw with sensory innervation.