Facial Nerve GN PDF

Facial Nerve Gulshana Choudhury Module: Oral and Dental Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management Intended Learning Outcomes Describe the func;on of the Facial nerve...

Facial Nerve Gulshana Choudhury Module: Oral and Dental Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management Intended Learning Outcomes Describe the func;on of the Facial nerve (VII) Outline the anatomical regions it supplies Explain the relevance of the Facial nerve to den;stry  Facial nerve - transmit information to and from facial structures Various branches allow sensation to oral and facial structures Production of saliva from sub mandibular and sub lingual saliva glands Why do I need to know this?  Acland's Video Atlas of Human Anatomy Resources Anatomy.tv Teach me Anatomy  7th paired cranial nerve Associated with 2nd pharyngeal arch Facial Nerve Emerges from brain between pons and medulla 2 roots Larger, main motor root from motor nucleus Smaller root or ‘nervus intermedius’ Passes into internal auditory meatus  Provides motor function to…. Motor Root FuncJons Stylohyoid muscle Stapedius (ear) Muscles of facial expression Posterior belly of digastric INCLUDING Platysma  Serves a few functions FuncJon - Nervus intermedius Special sensory Sensory Parasympathetic Taste of anterior External ear efferents Supplies many glands of head and neck 2/3 tongue Sublingual & submandibular Via chorda tympani salivary glands Saliva production Lacrimal, nasal, palatine & pharyngeal glands Anatomical Course Anatomically, the course of the facial nerve can be divided into two parts: Intracranial – the course of the nerve through the cranial cavity, and the cranium itself Extracranial – the course of the nerve outside the cranium, through the face and neck. Intracranial The nerve arises in the pons, an area of the brainstem It begins as two roots; a large motor root, and a small sensory root Two roots travel through the internal acous;c meatus into the facial canal  Of intracranial 3 branches before leaving facial canal Greater petrosal nerve – parasympathe;c Obres to mucous glands of nose, paranasal sinuses and palate, and lacrimal gland for tear produc;on. Nerve to stapedius – motor Obres to stapedius muscle of the middle ear for dampening down loud noises. Chorda tympani – special sensory Obres to the anterior 2/3 tongue (taste func;on) and parasympathe;c Obres to the submandibular and sublingual glands. Then facial nerve exits facial canal (and the skull) via the stylomastoid foramen Chorda tympani Innervates the anterior 2/3 of the tongue with the special sense of taste Travels with the lingual nerve (branch of trigeminal nerve) Also carries parasympathe;c Obres to the submandibular and sublingual glands.  Nerve leaves the cranial vault and enters on the face Extracranial The facial nerve exits the cranium via the stylomastoid foramen Extracranial branches Posterior auricular nerve Posterior belly of the digastric muscle Stylohyoid muscle Passes through the paroJd gland and terminates into 5 branches 3 Temporal branch Zygoma;c branch Buccal branch 5 branches; Supply motor function to muscles of facial expression Marginal mandibular branch Cervical branch Posterior Auricular Nerve Motor nerve Ascends in front of the mastoid process Innervates the intrinsic and extrinsic muscles of the outer ear It also supplies the occipital part of the occipitofrontalis muscle.  Posterior belly of digastric muscle Responsible for raising hyoid bone Innervates stylohyoid muscle Nerves to digastric and stylohyoid muscle  Facial nerve terminates and branches into 5 terminal branches within parotid gland Facial branches All responsible for providing motor function to muscles of facial expressions Two Ten Zebras Zebras Bit Buggered My My Cat Car Muscles of Facial Expression Temporal Branch Leave superior surface of paro;d gland Cross zygoma;c arch to reach forehead Supplies: o Auricular muscles o Frontalis o Orbicularis oculi o Corrugator supercilii ZygomaJc Branch Usually 2 – upper & lower Upper branch passes above orbit to supply frontal belly of occipitofrontalis muscle & orbicularis oculi Lower branch passes below to supply lower part of orbicularis oculi & contributes to innerva;on of muscles in the upper lip & nose Buccal Branch Usually 2 Supplies the orbicularis oris, buccinator and zygomaJcus Contributes to innerva;on of muscles of upper lip & nose Mandibular Branch Emerges from lower border of paro;d gland Runs near inferior border of mandible Supplies muscles of lower lip Depressor labii inferioris Depressor anguli oris Mentalis Cervical Branch Passes downwards from the lower border of the paro;d gland Supplies platysma muscle Raises the skin of the neck to form no;ceable ver;cal and horizontal ridges and depressions Can pull the corner of the mouth down, as when a person grimaces. Damage to the facial nerve - Intracranial lesions Intracranial lesions occur during the intracranial course of the facial nerve (proximal to the stylomastoid foramen) Muscles of facial expression can be paralysed or be extremely weakened Causes Infec;on related to the external or middle ear Stroke Symptoms depend on location and branches it affects Paralysis of muscles of facial expression  Most common cause of intracranial lesion of facial nerve - infection related to external or middle ear If affects nerve such as chorda tympani If no causes can be found, the term Bell’s palsy is usually used. Dry eye, dry mouth, loss of taste, diUculty talking Reduced lacrimal function Reduced salivation Hyper sensitive to sound Loss of taste on the anterior 2/3 of the tongue Damage to the facial nerve - Extracranial lesions Nerve has exit the stylomastoid foramen ONLY motor function effected Paralysis or severe weakness of Can be due to pressure - forceps delivery Idiopathic - no cause - bell’s palsy the muscles of facial expression Various causes ParoJd gland pathology – e.g a tumour, paro;;s, surgery. Inflammation InfecJon of the nerve – par;cularly by the herpes virus Local anaesthe;c (rare) When anaesthetic wears off, the muscles of facial expression can regain normal function  Can have facial nerve damage weakness after surgery ParoJd gland tumour and surgery Summary Of facial nerve: Motor supply to muscles of facial expression Minor sensory role Taste to anterior two-thirds of tongue Parasympathe;c innerva;on to: submandibular and sublingual salivary glands nasal, pala;ne and pharyngeal mucous glands lacrimal glands https://app.sli.do/event/eonQVofQQwcE41KTzieRzC References h\ps://teachmeanatomy.info/head/cranial-nerves/facial-nerve/ h\ps://www.anatomy.tv/;tles h\ps://aclandanatomy.com/ Norton, N.S. and Ne\er, F.H. (2017) Ne#er's head and neck anatomy for Den4stry. Elsevier (Chapter 5) Liebgo\, B. (2018) The anatomical basis of Den4stry. PHILADELPHIA (U.A.): SAUNDERS.