BMS2-7 Cranial Nerve V - Trigeminal PDF

Trigeminal Nerve +1 Trigeminal Nerve • Emerges from lateral aspect of ventral pons by a large sensory root & a small motor root • Sensory root posterolateral to motor root Trigeminal Nerve is the General Sensory Nerve for the Head • The principal somatosensory nerve for the head • Afferents arr...

Trigeminal Nerve +1 Trigeminal Nerve • Emerges from lateral aspect of ventral pons by a large sensory root & a small motor root • Sensory root posterolateral to motor root Trigeminal Nerve is the General Sensory Nerve for the Head • The principal somatosensory nerve for the head • Afferents arrive thru its ophthalmic, maxillary & mandibular divisions • Afferent fibers have cell bodies in trigeminal ganglion • Central processes of all primary afferents end either in: - main sensory nucleus (caudal pons) or - spinal trigeminal nucleus (medulla to upper spinal cord) • Mesencephalic nucleus: Proprioception from muscles of mastication & periodontium • Motor nucleus : Mid pons. Muscles of mastication Trigeminal Nerve is the General Sensory Nerve for the Head • Central processes of all primary afferents end either in: - main sensory nucleus or - spinal trigeminal nucleus Trigeminal Nerve General Sensory Afferents • Sensory root of CN V composed of central processes of pseudo-unipolar neurons of trigeminal ganglion Trigeminal ganglion (a.k.a. Gasserian,a.k.a Semilunar): • Lies in trigeminal impression on temporal b. • On anterolateral surface of apex of temporal b. • Posteromedial to foramen ovale of sphenoid b. • Flattened & crescent shaped • Peripheric processes of its neurons (pseudounipolar) form opthalmic n, maxillary n. & sensory part of mandibular n. Trigeminal Nerve General Sensory Afferents Trigeminal Ganglion (Gasserian, Semilunar): • Housed within a dural recess (trigeminal cave) lateral to cavernous sinus • Corresponds w/ dorsal root ganglion of a spinal nerve • Contains cell bodies of pseudo- unipolar 1st sensory neurons • Lies about 5 cm deep to pre-auricular point • Is semilunar w/ convex margin directed forward & laterally • Dural pouch in which it is contained : Cavum trigeminale, a.k.a. Meckel’s Cave • Roof of cave formed by 2 meningeal layers, floor by 1 meningeal & 1 endosteal layer Trigeminal Nerve General Sensory Afferents Trigeminal Ganglion (Gasserian, Semilunar): Trigeminal Nerve General Sensory Afferents Trigeminal Ganglion Communications: • Receives fibers from sympathetic plexus around internal carotid artery • Gives meningeal twigs (very small branches) to tentorium cerebelli & floor of middle cranial fossa Trigeminal Ganglion Branches: 1. Peripheral branches: • Peripheral processes of neurons of the gangion • Form ophthalmic, maxillary & sensory parts of mandibular n. • These pierce cavum trigeminale • Are attached to convex margin of ganglion 2. Central branches: • Central processes of neurons of ganglion • Form sensory root which is attached to concave margin of ganglion • Sensory root passes backward & medially • Is attached to ant. surface of pons at its junction w/middle cerebellar peduncle Trigeminal Nerve General Sensory Afferents • Trigeminal ganglion general sensory afferents cover • Most of face • Scalp up to lambdoid suture • Oral cavity • Nasal cavity • Teeth • TMJ • Nasopharynx • Auricle • Part of external acoustic meatus • Part of dura mater • Additionally proprioceptive inputs from • Muscles of mastication • Muscles of facial expression • Extraocular eye muscles Trigeminal Nerve General Sensory Afferents • Spinal nerve dermatome maps (sensory innervation of body/skin) resemble map of zones of cutaneous innervation by 3 divisions of CN V (peripheral nerve fields) • HOWEVER there is little overlap in innervation by CN V divisions ➔ lesions of a single nerve result in clearly demarcated areas of numbness • Peripheral nerve fields not horizonal. Curve upward • Embryologically, facial skin grows upward with growth of brain & skull • Each division of trigeminal n. associated w/a developing facial process which gives rise to a specific area of adult face : • Opthalmic n associated w/frontonasal process • Maxillary n associated w/maxillary process • Mandibular n associated w/mandibular process Trigeminal Nerve General Sensory Afferents Cutaneous Innervation of Face & Neck Showing Dermatomes Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – General Comments • Not a branchial nerve derivative (in contrast to CN V 2 and CN V 3) • Serves structures derived from paraxial mesoderm of embryonic frontonasal process • Ophthalmic nerve’s association with the other CN V divisions is a secondary occurrence • Somatic (general) sensory fibers • Cutaneous distribtion: Skin over forehead, much of nose, conjunctiva Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course • Leaves trigeminal ganglion from its anteromedial aspect • Pierces dura mater & enters cavernous sinus • Courses below trochlear n. & oculomotor n. in cavernous sinus • Leaves cavernous sinus & exits skull thru sup. orbital fissure Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches • At level of sup. orbital fissure gives off : (1) Recurrent meningeal branch (tentorial nerve) • Then separates into: (2) Lacrimal n. (3) Frontal n. (4) Nasociliary n. • Fibers from oculomotor n, trochlear n & abducens n are thought to combine w/opthalmic n. fibers, carrying proprioceptive afferents from extraocular muscles • Fibers from int. carotid plexus also combibe w/CN V1 fibers Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (2) Lacrimal Nerve • Courses on sup border of lat rectus m together w/ lacrimal artery • Passes thru lacrimal gland • Terminal branches pierce orbital septum & end in upper eyelid • Carries GSA from: • Conjunctiva adjoining lacrimal gland • Upper eylid • Serves as carrier for postsynaptic parasympathetic secrotomotor fibers to lacrimal gland coming from pterygopalatine ganglion via zygomaticotemporal n (branch of maxillary n.) -GVE(*) See page for lacrimal gland innervation Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (3) Frontal Nerve • Largest division of opthalmic n. • May be regarded as its continuation both from its size & direction • Enters orbit thru sup. orbital fissure • Does not run within tendinous ring • Runs above levator palpebrae superioris m. ➔ divides into its 2 terminal branches: Supraorbital n. • Leaves orbital cavity thru supraorbital foramen • Innervates upper eyelid skin & conjunctiva • Then divides into its terminal branches : Lateral branch & medial branch → innervate skin on forehead up to lambdoid suture & mucosa lining frontal sinus Supratrochlear n. • Passes over trochlea (of sup oblique m.) Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (3) Frontal Nerve: Runs above levator palpebrae superioris m. 1. Supraorbital n. ➔ divides into its 2 terminal branches: 2. Supratrochlear n. • Leaves orbital cavity thru supraorbital foramen • Innervates upper eyelid skin & conjunctiva • Then divides into its terminal branches : Lateral branch & medial branch → innervate skin on forehead up to lambdoid suture & mucosa lining frontal sinus Opthalmic Nerve CN V 1 – Course & Branches (3) Frontal Nerve - branches: 2. Supratrochlear n. • • • • • Passes over trochlea (pulley of sup. oblique m.) Courses medial to suprorbital n. Innervates: Skin of infero-medial forehead Conjunctiva & skin of upper lid Trigeminal Nerve General Sensory Afferents Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (4) Nasociliary Nerve: • Enters orbit thru common tendinous ring • Crosses optic n. & passes to medial side of orbit • Courses anteriorly btwn medial rectus m. & sup oblique m. • Gives - communicating branch to ciliary ganglion (long root of the ciliary ganglion) - post. ethmoidal n. - long ciliary n. • And terminates by giving off - infratrochlear n. - ant. ethmoidal n. Leaves nasociliary n. as 2-3 twiglets, distributes on ciliary body, cornea & iris Within it also travel postganglionic sympathetic fibers coming from sup. cervical ganglion via int. carotid plexus (*) → dilator pupilla m. These fibers leave ciliary ganglion WITHOUT synapsing. GSA only Join the short ciliary nerves & distribute along eyeball Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (4) Nasociliary Nerve: - communicating branch to ciliary ganglion (long root of the ciliary ganglion) - long ciliary n. Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 – Course & Branches (4) Nasociliary Nerve: • Gives - communicating branch to the ciliary ganglion (long root of the ciliary ganglion) - post. ethmoidal n. - long ciliary n. • And terminates by giving off - infratrochlear n. - ant. ethmoidal n. Passes thru ant. ethmoidal foramen & enters cranial cavity Passes anteriorly over cribriform plate Sends sensory fibers to meninges, ant ethmoidal air cells Enters nasal cavity thru opening by crista galli (nasal slit) Here gives branches : Internal nasal branches : to mucosa of nasal septum & lateral wall of cavity External nasal branches : Nasal vestibule, alae nasi, tip (apex) Passes thru post. ethmoidal foramen Distributes along post ethmoidal air cells & mucosal lining of sphenoidal sinus Courses on top of medial rectus m. Passes under trochea & leaves orbit Innervates - GSA - superior lateral part of skin of dorsum of nose, lacrimal sac, lacrimal caruncle, skin of lower eyelid & conjunctiva Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 2. Lacrimal n. 3. Frontal n. 4. Nasociliary n. Trigeminal Nerve General Sensory Afferents Opthalmic Nerve CN V 1 Clinical Correlate: Testing CN V1: • Integrity is tested by checking corneal reflex —touching the cornea, which is also supplied by CN V1, with a wisp of cotton will evoke a reflexive blink if nerve is functional Trigeminal Nerve General Sensory Afferents Maxillary Nerve CN V 2 – General Info • Innervates derivatives of maxillary prominence of 1st pharyngeal arch • Sensory only • Exits cranial cavity via foramen rotundum • General sensory fibers distributed to skin & mucous membranes associated w/upper jaw • Lower eyelid & its conjunctiva • Cheeks • Nasal cavity & lateral nose • Upper lip • Upper molars, incisors, canine teeth & associated gingiva • Superior palate • Roof of the pharynx, the maxillary, ethmoid and sphenoid sinuses, and parts of the meninges Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Course • Leaves trigeminal ganglion btwn opthalmic n. & mandibular n. • Courses anteromedially • Gives off middle meningeal n. in midddle cranial fossa – GSA to dura mater • Enters cavernous sinus & travels under opthalmic n. • Exits cavernous sinus, passes thru foramen rotundum & exits cranium Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Course • All extracranial branches given off in pterygopalatine fossa • Branches can be subdivided into: - those that come directly from maxillary n. (main trunk) - those associated w/paraysmpathetic pterygopalatine ganglion • Named branches from main trunk: - Meningeal Ganglionic Zygomatic Posterior, middle & anterior superior alveolar Infraorbital • Named branches from pterygopalatine ganglion: - Orbital Nasopalatine Post. sup. nasal Greater (ant) & lesser (post) palatine Gray’s version 39th Edition Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Course • After exiting cranium → enters pterygopalatine fossa • Courses straight in upper part of fossa • On post surface of fossa enters sup. orbital fisssure & exits • Turns medially to enter infraorbital canal of maxilla • Becomes infraorbital n. →considered to be direct continuation of maxillary n. • Exits orbit thru infraorbital foramen Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Course Gray’s version 39th Edition • Gives meningeal branch in middle cranial fossa • Exits cranium via foramen rotundum→ enters upper part of pterygopalatine fossa • As it crosses fossa gives 2 large ganglionic branches –> contains fibers destined for nose, palate, pharynx These pass thru pterygopalatine ganglion w/o synapsing • Inclines sharply laterally on post. surface of orbital process of palatine bone & on upper part of post. surface of maxilla in inf. orbital fissure (inf orbital fissure posteriorly connects w/pterygopalatine fossa) • Lies outside orbital periosteum • Gives off zygomatic brach, then post. sup. alveolar branches • Halfway btwn orbital apex & rim, turns medially to enter infraorbital canal as the infraorbital n. Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Branches Given Off in Pterygopalatine Fossa Zygomatic n. • Branches from maxillary n. at pterygopalatine ganglion- fibers exit w/o synapsing • Enters orbit thru inferior orbital fissure • Divides at back of orbital cavity into 2 branches: • Zygomaticotemporal n. supply skin of temple – passes thru zygomatic bone → temporal fossa → distributes & ends here • Zygomaticofacial n. : inferiorly situated & supplies skin of cheek • These 2 branches exit orbit using same named foramina Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Branches Given off in Pterygopalatine Fossa Trigeminal Nerve Hitchike for PS Maxillary n. CN V 2 - Branches Given off in Pterygopalatine Fossa Zygomaticotemporal n. - Hitchike Function • Post-ganglionic parasympathetic fibers originating in facial nerve & pterygopalatine ganglion • Then they join lacrimal nerve (branch of ophthalmic division of trigeminal n.) - another hitchike GVE - secretomotor • These fibers eventually provide innervation to lacrimal gland Trigeminal Nerve General Sensory Afferents Superior Alveolar Nerves • Branches off either in pterygopalatine fossa or in infraorbital groove or canal • Usually 2 or 3 • Courses antero-inferiorly & pierces infratemporal surface of maxilla • Descends under muscosa of maxillary sinus • Divides into small branches → these branches link up to form molar part of superior alveolar plexus → twigs to upper molar teeth → branch to upper gingiva & adjoining cheek Trigeminal Nerve General Sensory Afferents Posterior Superior Alveolar N. • Branches off main trunk of maxillary n. just before it enters infraorbital Groove • Descends on maxillary tuberosity • Enters post. alveolar canals on infratemporal surface of maxilla • Communicates w/middle superior alveolar n. • Gives branches to mucosa of maxillary sinus molars, & corresponding gingiva • Branches enter apical foramina at roots of teeth • Passes thru canaliculi in lateral wall of maxillary sinus in 62% of cases, or under mucous membrane of sinus in 38% cases Trigeminal Nerve General Sensory Afferents Posterior Superior Alveolar nerve • In cases, where middle sup. alveolar n. is absent, premolars also innervated by post. sup. alveolar n. • Number can vary from single to multiple • On reaching molar teeth, post. sup. alveolar n. gives rise to 4 groups of terminal branches: — Dental branches, supply molar & premolar roots; — Alveolar branches, to alveolar periosteum & gingival mucosa; — Mucous branches, to maxillary sinus mucosa; — Bone branches to maxilla Trigeminal Nerve General Sensory Afferents Posterior Superior Alveolar Nerve Trigeminal Nerve General Sensory Afferents Branches Given off in Infraorbital Canal Middle & Anterior Superior Alveolar Nerves • If present, middle superior alveolar n. branches off infraorbital n. in infraorbital canal • Runs in lateral wall of maxillary sinus & supplies premolars • Most of the time a plexus (branches from either or all superior alveolar n.n.) supply teeth rather than a unified nerve • Ant. sup. alveolar n. leaves infraorbital n. in the orbital groove — the posterior part of infraorbital canal • Enters ant. wall of maxillary sinus & there divides into branches supplying incisors & canine teeth • Runs further towards canine fossa branching and forming the superior dental plexus (with the branches of the middle alveolar n. if present) in the maxillary alveolar process • From this plexus nasal branches arise • Passes thrua small canal in lateral wall of inferior meatus of nose, supplies mucous membrane of anterior area of lateral wall & floor of nasal cavity • Ant sup alveolar n has the form of a single trunk in 75% of cases, and in 25% it forms a small plexus from its terminal branches, which overlays the canine fossa Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Greater & Lesser Palatine Nerves • Originate from pterygopalatine ganglion • Greater palatine n. descends thru greater palatine canal (mean canal length 31 mm, range 15–44 mm) • And the greater palatine foramen to run anteriorly in a groove on inferior surface of hard palate • Innervates hard palate and palatal gingiva • Lesser palatine n. (or nerves) descends thru lesser palatine foramen (or foramina) • Its branches innervate the uvula, tonsil & soft palate • These nerves anastomose w/ branches of glossopharyngeal n. to form a tonsillar plexus around the palatine tonsil Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Nasopalatine Nerve • Largest of the nasal branches originating from the pterygopalatine ganglion • Enters nasal cavity thru sphenopalatine foramen • Reaches nasal septum & runs anteriorly & inferiorly btwn the periosteum & mucous membrane of nasal septum • Exits nasal cavity through incisive foramen • Its terminal branches innervate mucosa of ant. part of hard palate & palatal gingiva near canine teeth • Terminal branches may communicate w/branches of greater palatine n. • In some cases the nasopalatine n. can innervate the incisor teeth, thus making the nasopalatine nerve block necessary to complete the anaesthesia of the central incisor Trigeminal Nerve General Sensory Afferents Maxillary n. CN V 2 - Branches Given off in Face • Through infraorbital foramen, emerges on face btwn levator labii superioris m & levator anguli oris m. • After exiting thru infraorbital foramen, divides into 4 branches — inferior palpebral, the external nasal, the internal nasal and the superior labial branches for the sensory innervation to skin of eyelid, nose, cheek & upper lip Mandibular Nerve CN V 3 • Largest of 3 divisions of trigeminal nerve • Small motor root & larger sensory root • Components: Sensory, branchial motor • Sensory: Skin over mandible, teeth & gingiva of mandible, lower lip, fleshy part of cheek, part of auricle incl. external meatus & auricle, tympanic membrane, part of temple, mucosa of presulcal part of tongue, floor of oral cavity • Motor : Muscles of mastication 42 Mandibular Nerve CN V 3 Course: • Exits cranial cavity thru foramen ovale & courses thru infratemporal fossa • As it descends from foramen ovale, is usually app. 4cm from surface & slightly ant. to neck of mandible • Passes btwn tensor veli palatini (medial) & lateral pterygoid m (lateral) • Gives off meningeal branch & n. to medial pterygoid from its medial side • Divides into small anterior trunk & large posterior trunk • Ant. trunk: Branches to 4 main muscles of mastication + buccal branch, sensory • Post. trunk: 3 sensory branches & a motor branch Auriculotemporal Lingual Inferior alveolar + motor to mylohyoid & ant. belly of digastric 43 Mandibular Nerve CN V 3 Meningeal branch a.k.a. n. spinosus • From main trunk before division • Re-enters cranium thru foramen spinosum together w/middle meningeal artery • Sensory supply to dura mater in middle cranial fossa • To a lesser extent, also suppies ant. cranial fossa & calvarium 44 Mandibular Nerve CN V 3 Nerve to Medial Pterygoid • • • • Before branching into its 2 main trunks Enters deep aspect of medial pterygoid m. Few filaments pass thru otic ganglion w/o synapsing Supply tensor tympani & tensor veli palatini mm 45 Mandibular Nerve CN V 3 46 47 Mandibular Nerve CN V 3 From Anterior Trunk Buccal Nerve • Sensory to cheek – skin over buccinator, buccal mucous membranes, buccal gingiva adjacent to 2nd & 3rd molars • Passes btwn 2 heads of lat pterygoid • Descends deep to tendon of temporalis • Passes laterally in front of masseter • Anastomoses w/buccal branches of facial n. • Motor fibers to lat. pterygoid m. 48 Mandibular Nerve CN V 3 From Anterior Trunk Nerve to Masseter • Crosses post. part of mandibular notch together w/masseteric a. • Branches off on masseter & enters its deep surface • Provides articular branches to TMJ 49 Mandibular Nerve CN V 3 From Anterior Trunk Deep Temporal Nerves • Pass above lat. pterygoid & enter deep surface of temporalis m. 50 Mandibular Nerve CN V 3 From Anterior Trunk Nerve to Lateral Pterygoid • Enters deep surface of lat. pterygoid 51 Mandibular Nerve CN V 3 Posterior Trunk • Larger than ant trunk • Mainly sensory, except for fibers in nerve to mylohyoid • Divides into: - Auriculotemporal - Lingual - Inferior alveolar 52 Mandibular Nerve CN V 3 From Posterior Trunk Auriculotemporal Nerve - Course • Has 2 roots encircling middle meningeal a. • Passes btwn sphenomandibular lig. & neck of mandible • Runs lateraly behind TMJ related to upper part of parotid • Emerges onto face behind TMJ within sup. surface of parotid • Divides into superficial temporal branches 53 Mandibular Nerve CN V 3 From Posterior Trunk Auriculotemporal Nerve • Communicates w/ facial n. • Sends usually 2 branches passing behind neck of mandible & joining facial n. at post. border of masseter • Communicates w/otic ganglion • Filaments from otic ganglion join auriculotemporal n. close to its origin CN IX → Lesser petrosal n. → synapse on otic ganglion → join auriculotemporal n. → carrier for postganglionic PS secretomotor to parotid gland 55 56 Mandibular Nerve CN V 3 Auriculotemporal Nerve – Sensory Distribution on Face • Cutaneous branches supply tragus, part of adjoining auricle, post. part of temple Clinical Correlate: • May be damaged during parotid gland surgery → impaired sensation of tragus & temple 57 Mandibular Nerve CN V 3 From Posterior Trunk Lingual Nerve • Mucosa of ant 2/3rds of tongue, floor of mouth, mandibular lingual gingiva – excluding circumvallate papilla • First, runs beneath lat pterygoid & superficial to tensor veli palatini • Here, it is joined by chorda tympani branch of facial n. • Crosses lingual sulcus beneath mucosa • Here, lies on deep portion of submandibular gland Crosses below submandibular duct • Curves upwards, forwards & medially to enter tongue by medial & lateral branches 58 Mandibular Nerve CN V 3 From Posterior Trunk Lingual Nerve • Within tongue: -Medial branch sends small branches to medial part of ventrolateral tongue - Lateral branch runs along lat border of tongue - Sends larger branches to mucosa of ant. tip of tongue 59 Mandibular Nerve CN V 3 From Posterior Trunk Lingual Nerve • Connected to submandibular ganglion by 2 or 3 branches • Forms connecting loops w/twigs of hypoglossal n. at ant margin of hyoglossus & within tongue Inf alveolar n. Lingual n. Hyoglossal n. Sublingual a. Submental a. 60 Coronal Section Thru Tongue, Mouth & Body of Mandible Opposite 1st Molar Tooth 61 Mandibular Nerve CN V 3 From Posterior Trunk Lingual Nerve - Clinical Correlate • Lingual n. needs to be protected (at risk) during surgical removal of impacted lower 3rd molars • Lingual n. also at risk during surgical removal of submandibular gland bcs duct must be dissected from lingual n. & bcs its connection to submandibular ganglion pulls it into the operating field 62 Mandibular Nerve CN V 3 From Posterior Trunk Inferior Alveolar Nerve • Carries both sensory & motor fibers Course in Infratemporal Fossa • Descends behind lat. pterygoid m. • At lower border of lat. pterygoid, passes btwn sphenomandibular lig & ramus of mandible • Below lat pterygoid it is accompanied by inf alveolar a. (branch of 1st part of maxillary a). 63 Mandibular Nerve CN V 3 From Posterior Trunk Inferior Alveolar Nerve Just before entering mandibular canal, gives off small branch : Mylohyoid Nerve • Mylohyoid n pierces sphenomandibular lig • Follows course app. paralell to lingual n. • Lies on superficial surface of mylohyoid, btwn mylohyoid & ant belly of digastric • Supplies mylohyoid m. & ant. belly of digastric • Gives few fibers to supply skin over point of chin 64 Mandibular Nerve CN V 3 From Posterior Trunk Inferior Alveolar Nerve • Enters mandibular canal via mandibular foramen • Inf alveolar a. & v. also enters mandibular canal • Runs downwards & forwards in canal, below apices of teeth until below 1st & 2nd premolars • Here, divides into terminal branches: incisive & mental 65 Mandibular Nerve CN V 3 From Posterior Trunk Inferior Alveolar Nerve : Terminal branches: Incisive & Mental Incisive Nerve: • Continues forward in a bony canal OR as a plexus • Gives off branches to 1st premolar, canine, incisor & associated labial gingiva • Central incisors (mandibular) receive bilateral innervation, (fibers maybe crossing mid-line wihin periosteum to re-enter bone via numerous canals in labial cortical plate) Mental Nerve: • Passes upwards, backwards & outwards • Emerges via mental foramen below & btwn apices of premolars • Divides into 3 branches • 2 pass upwards to form incisor plexus, labial to teeth – supplies gingiva & periosteum • 3rd branch passes upwards btwn intermingled muscle fibers of depressor anguli oris & platysma • Supplies skin of lower lip & chin 66 Mandibular Nerve CN V 3 Summary - Branches • From main trunk before division • Muscular branches : Med. pterygoid, tensor tympani & tensor veli palatini mm motor • Meningeal branch, a.k.a. n. spinosus sensory • From anterior division • Masseteric n. • Deep temporal nn. ant. & post. • Buccal n. • Lateral pterygoid n. • From posterior division • Auriculotemporal n. • Lingual n. • Inferior alveolar n. -Mylohyoid n. - Incisive - Mental motor motor sensory motor sensory sensory mixed motor sensory sensory 67 Mandibular Nerve CN V 3 Hitchhike Functions • Acts as a carrier for special sensory and autonomic fibers belonging to chorda tympani, a branch of facial nerve (CN VII) • Chorda tympani branches from facial n. in region of middle ear • Carries pre-synaptic parasympathetic fibers which join lingual n. • Special sensory fibers carried w/ lingual nerve provide taste to ant. 2/3rds of tongue • PS fibers fibers synapse in submandibular ganglion, then innervate submandibular & sublingual glands via lingual n.secretomotor • Autonomic innervation of parotid gland originates from CN IX – glossopharygeal, parasympathetic • Auriculotemporal nerve transmits post-synaptic axons from otic ganglion to parotid gland. 68 Mandibular Nerve CN V 3 69 Trigeminal – Facial Nerve Connections Proprioception • Proprioception: Quality of mechanosensibility that informs CNS about static & dynamic conditions of muscles and joints • Originates in specialized sensory organs (proprioceptors) : Muscle spindles, Golgi tendon organs, capsular joint mechanoreceptors, some cutaneous mechanoreceptors • Proprioception applies for all skeletal muscles • Facial proprioception plays a key role in facial expression, coordination of facial movement, regulation of masticatory force in conjunction with jaw muscles, and in orofacial reflexes related to speech, swallowing, cough, vomiting, or breathing • Proprioception of all the facial & masticatory muscles depends on CN V – mostly mandibular n. • Connections btwn CNV and CNVII explain, a in part, how trigeminal afferents transmit proprioceptive information from the face to the mesencephalic trigeminal nucleus for processing 70 71