Head and Neck 7: Innervation of the oral region

• The trigeminal nerve is the major sensory nerve of the head and is divided into three major parts (ophthalmic, mandibular, maxillary)
• The mandibular nerve also has a motor component that supplies the muscles of mastication
• The ophthalmic nerve (CNV1) enters the orbit via the superior orbital fissure and splits into three major branches: lacrimal, frontal, and nasociliary
• The lacrimal nerves goes to the lacrimal gland
• The frontal nerve travels to the forehead and further branches into supraorbital and infratrochlear nerves
• The nasociliary nerve pierces the medial wall of the orbit and reaches the sinuses and nasal cavity; it supplies the cornea and is therefore the sensory limb of the blinking reflex
• The maxillary nerve (CNV2) enters the pterygopalatine fossa through the foramen rotundum
• The maxillary nerve gives off eight major branches: nasopalatine, infraorbital, zygomatic, posterior superior alveolar, greater palatine, lesser palatine, nerve of pterygoid canal, nerve of pharyngeal canal
• The infraorbital nerve travels through the infraorbital groove and canal and emerges from the infraorbital foramen to give off the anterior and middle superior alveolar nerves, which supply the anterior teeth and adjacent gingiva
• The posterior superior alveolar nerve supplies the posterior maxillary teeth
• The greater and lesser palatine nerves descend to the hard palate through the palatine canal and emerge near the hamulus of the sphenoid, innervating the hard and soft palate respectively
• The nerve of pterygoid canal is formed by the convergence of the greater petrosal and deep petrosal nerves
• The nasopalatine is a medial nerve that eventually reaches the incisive canal in the hard palate
• The mandibular nerve (CNV3) enters the infratemporal fossa through the foramen ovale and forms four major branches: auriculotemporal, buccal, lingual, and inferior alveolar
• The inferior alveolar nerve enters the mandible and supplies the mandibular teeth (forms the inferior dental plexus)
• Before the inferior alveolar enters the mandible, it gives off the nerve to mylohyoid and anterior belly of digastric
• Inside the mandible, the inferior alveolar nerve splits into the incisive (supplies teeth) and mental (supplies lower lips)
• The lingual nerve transmits sensation and taste; taste is transmitted back through the chorda tympani from the facial nerve
• The facial nerve enters the temporal bone through the internal acoustic meatus and splits into three major branches: greater petrosal, chorda tympani and main trunk
• The greater petrosal nerve travels to the front and is joined by deep petrosal nerves to form the nerve of the pterygoid canal
• The chorda tympani travels to the infratemporal fossa via the petrotympanic fissure and joins the lingual nerve; its fibers eventually reach the submandibular ganglion and innervate both submandibular and sublingual glands
• The main trunk of the facial nerve exits the temporal bone through the stylomastoid foramen, pierces the parotid gland and splits into five branches to innervate the muscles of facial expression with motor fibers (temporal, zygomatic, buccal, mandibular, cervical)
• The glossopharyngeal nerve emerges from the region of the carotid sheath and travels to the front, deep to the hyoglossus muscle, to reach the floor of the mouth and supply the oropharynx and posterior 1/3 of the tongue
• The glossopharyngeal releases two important branches: tympanic nerve and nerve to carotid body and sinus
• Tympanic nerve enters the temporal bone and becomes in the tympanic plexus in the middle ear; it then exits the temporal bone to become the lesser petrosal nerve and then enters the infratemporal fossa via the foramen ovale to join the otic ganglion
• The vagus nerve descends from the carotid sheath to the chest and abdomen, supplies most muscles of the soft palate, pharynx, and larynx, as well as the mucosa and general sensation of the larynx
• Vagus nerve gives off two major branches: the superior laryngeal and recurrent laryngeal
• The hypoglossal nerve travels to the floor of the mouth by travelling laterally to the hyoglossus muscle to reach the floor of the mouth along with the lingual nerve
• Hypoglossal supplies most of the muscles of the tongue, except for the palatoglossus which is supplied by the vagus nerve
• The upper lip is supplied by the infraorbital nerve (from maxillary) an the lower lip is supplied by the mental nerve (from inferior alveolar)
• The cheek is supplied by the buccal nerve from the mandibular nerve (main trunk of the facial nerve also gives off a buccal branch, but it is motor rather than sensory)
• Anterior 2/3 of the tongue receives general sensation from the mandibular nerve and taste from the facial nerve via the chorda tympani
• Posterior 1/3 of the tongue receives general sensation and taste from the glossopharyngeal nerve
• Hypoglossal nerve innervates most muscles of the tongue (intrinsic muscles, genioglossus, hyoglossus, styloglossus) but the palatoglossus is innervated by the vagus nerve
• The hard palate is innervated by the greater palatine nerve and the nasopalatine nerve, which innervates the anterior mucous membrane
• The soft palate is innervated by the lesser palatine nerve
• Parasympathetic supply of the parotid gland is through the otic ganglion, which is supplied by the glossopharyngeal nerve
• Parasympathetic supply of the submandibular and sublingual glands is through the submandibular ganglion, which is supplied by the facial nerve
• Sympathetic innervation is via the superior cervical ganglion
• Tongue innervation

  A) mandibular nerve

  B) lingual nerve

  C) facial nerve

  D) chorda tympani

  E) glossopharyngeal nerve

  F) hypoglossal nerve

  G) vagus nerve