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Anatomy Revision |
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CRANIAL NERVES (Function + how to examine..)
I. Olfactory - smell, olfactory bulb –cribriform plate, anterior cranial fossa Anosmia – test with orange or peppermint oil (unilateral often unnoticed by patient, bilateral common after head injuries; often complain of loss of taste)
II. Optic – vision, medial ½ of L. eye goes to R. ½ of brain – optic chiasma, Visual acuity tested with Snellen chart, Blindness If complete lesion of one optic nerve = eye totally blind, no pupil constriction in affected eye and no consensual reflex in unaffected eye – Impaired pupil response However, when light shone into unaffected eye – PERL seen in both eyes, even though one eye is sightless.
III. Oculomotor - Motor- extra-ocular muscles (not SO/LR) –Diplopia -Eye looks Down + Laterally -Movements impaired - levator palpebrae superioris (Ptosis eyelid) - ciliary muscle - Parasymp.- ciliary ganglion Pupil dilation (direct and consensual reflexes lost)
IV. Trochlear - Motor- Sup. Oblique – Diplopia worse on DOWN + IN
V. Trigeminal (1st branchial arch, largest CN) -Motor – Muscles of mastication -Sensory – Face (Not angle of jaw), Scalp, Mucosa, Conjunctiva, Ant 2/3tongue, teeth -Parasymp.-SM gg – SM + SL glands, Lacrimal glands
Va – Ophthalmic (Sup.orb.fissure) Lacrimal, Frontal –Supra-trochlear + Supra-orbital, Infra-trochlear, Nasociliary-External Nasal (LaSSIE)
Vb – Maxillary (Rotundum) Infra-orbital, Zygomatico-facial + Zygomatico-temporal (IZZ)
Vc – Mandibular (Ovale) Nerve to Med Pterygoid, Meningeal branch, Lat.Pterygoid, Temporalis, Masseter, Buccal, Auriculotemporal, Lingual (Chorda Tympani-7) , I DN, (**Mylohyoid, Ant.belly Diagastric**)
*Test = Corneal reflex, Open jaw against resistance, Jaw jerk, Touch/pain –sensation over face VI. Abducens - Motor- Lat. Rectus – Diplopia worse on LATERAL gaze - Deviation of affected eye towards nose
VII. Facial (2nd branchial arch) -Motor – Facial expression muscles, Buccinator, Post.Digastric, Stylohyoid, Stapeius -Taste – Ant. 2/3 tongue -Parasymp. –Lacrimal, SM + SL glands 5 = Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical (accompanies CN8- Int. aud. Meatus, exits stylomastoid foramen)
*Test = Smile, screw eyes, whistle, show teeth, taste ant 2/3rds
VIII. Vestibulo-cochlear *Test = Balance + Hearing (tuning fork at 256Hz) -Sup./Inf. Vestibular, Cochlear nerves (Pt. complains of loss of hearing, vertigo, tinnitus)
IX. Glossopharyngeal (3rd branchial arch - Jugular foramen) -Taste – Post 1/3 tongue -Motor – Stylopharyngeus -Parasymp – Otic gg –Parotid gland -Sensory – Post 1/3 tongue, Pharynx, Tonsillar area, Carotid body + sinus *Test = Taste post 1/3 tongue, Reduced Gag reflex (9 +10), Voice may have nasal tone, Deviation of uvula
X. Vagus -Sensory – Pharynx, Larynx -Motor – Soft palate, Pharynx, Larynx -Parasymp. – Viscera thorax + Abdomen (Jugular foramen to carotid sheath, extensive distribution) *Test = Gag reflex (with 9), Hoarse voice (recurrent laryngeal nerve), Prolonged ‘Aagh’ –Soft palate moves to unaffected side, Vocalise sounds
XI. Accessory -Motor – SCM, Trapezius (spinal root) -Motor – Palatoglossus, Pharynx, Larynx, Levator veli palatine (cranial root) (Jugular foramen with 9 +10) *Test = Shoulder shrug, Turn head against resistance (weakness turning away from affected side)
XII. Hypoglossal -Motor – Tongue muscles (intrinsic + extrinsic – Not palatoglossus =11) - Branches to thyrohyoid, geniohyoid (Hypoglossal canal)
*Test = Impaired pronunciation (Dysarthria), Deviation of tongue to affected side on protrusion, Wasting
ANATOMY OF THE TONGUE Muscles - 4 Intrinsic - 4 Extrinsic (Hyo-, Genio-, Stylo-glossus 12; Palatoglossus 11) Blood supply – Lingual artery
Ant 2/3 -Motor –Hypoglossal (12) -Sensory -Lingual (Vc) -Parasymp. – Chorda tympani (7)
Post 1/3 -Motor –Hypoglossal (12) -Sensory –Glossopharyngeal (9) -Parasymp. – Glossopharyngeal (9)
MUSCLES OF MASTICATION Masseter (Vc) Origin: Zygomatic process of Maxilla Zygomatic arch Inserts: Lateral surface of angle/ramus of Mandible Elevation
Temporalis (Vc) Origin: Temporal bone, temporal fossa (fibres go beneath zygomatic arch) Inserts: Coronoid process Elevates + Retracts
Lateral Pterygoid (Vc) Origin: Infratemporal surface of Greater wing of Sphenoid (smaller) Lateral surface of Lat. Pterygoid plate of Sphenoid (bigger) (fibres run backwards) Inserts: Capsule + articular disc of TMJ Pterygoid fovea on Mandibular condyle (ant/inf to condyle head) Protrusion, Lat. Excursion, Assists depress/opening jaw
Medial Pterygoid (Vc) Origin: Medial surface of Lat. Pterygoid plate of Sphenoid (bigger) Maxillary tuberosity + neighbouring palating bone (fibres run backwards) Inserts: Medial surface of angle/ramus of Mandible Protrusion, Lat. Excursion, Elevation
Digastric (Vc + 7) Anterior (Vc) + Posterior (7) bellies connected by intermediate tendon Mastoid → tendon → digastric fossa Retracts + Depresses mandible
Mylohyoid (Vc) Mylohyoid line of mandible → Hyoid bone Depresses mandible, Raises FOM
Buccinator (7) Origin: Alveolar margins Max.+ Mand. molar teeth Pterygomandibular raphe, Pterygoid hamulus Inserts: Run forward to mingle with Orbicularis oris **Accessory M.o.M.**
(3 muscles which depress = Mylohyoid, Digastric, asst from Lat. Pterygoid)
INNERVATION OF TEETH
Maxillary (Maxillary N –Vb)
1 2 3 4 5 6 7 8
Mandibular (Mandibular N –Vc)
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Anna Dargue has written this overview of basic dental and facial anatomy. Cranial nerves, anatomy of the tongue, the muscles of mastication and innervation of teeth are outlined. Please refer to textbooks for detailed explanations. |