Facial Nerve Anatomy 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 application to patient management Intended Learning Outcomes Describe the function of the Facial ner...

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 application to patient management Intended Learning Outcomes Describe the function of the Facial nerve (VII) Outline the anatomical regions it supplies Explain the relevance of the Facial nerve to dentistry Why do I need to know this?  Acland's Video Atlas of Human Anatomy Resources Anatomy.tv Teach me Anatomy 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 Motor Root Functions Stylohyoid muscle Stapedius (ear) Muscles of facial expression Posterior belly of digastric Platysma Function - Nervus intermedius Special sensory Sensory Parasympathetic Taste of anterior External ear efferents 2/3 tongue Sublingual & submandibular salivary glands 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 acoustic meatus into the facial canal 3 branches before leaving facial canal Greater petrosal nerve – parasympathetic fibres to mucous glands of nose, paranasal sinuses and palate, and lacrimal gland for tear production. Nerve to stapedius – motor fibres to stapedius muscle of the middle ear for dampening down loud noises. Chorda tympani – special sensory fibres to the anterior 2/3 tongue (taste function) and parasympathetic fibres 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 parasympathetic fibres to the submandibular and sublingual glands. 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 parotid gland and terminates into 5 branches Temporal branch Zygomatic branch Buccal branch 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. Nerves to digastric and stylohyoid muscle Facial branches Two Ten Zebras Zebras Bit Buggered My My Cat Car Muscles of Facial Expression Temporal Branch Leave superior surface of parotid gland Cross zygomatic arch to reach forehead Supplies: o Auricular muscles o Frontalis o Orbicularis oculi o Corrugator supercilii Zygomatic 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 innervation of muscles in the upper lip & nose Buccal Branch Usually 2 Supplies the orbicularis oris, buccinator and zygomaticus Contributes to innervation of muscles of upper lip & nose Mandibular Branch Emerges from lower border of parotid 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 parotid gland Supplies platysma muscle Raises the skin of the neck to form noticeable vertical 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) Causes Infection related to the external or middle ear Stroke Paralysis of muscles of facial expression  Dry eye, dry mouth, loss of taste, difficulty talking Reduced salivation Loss of taste on the anterior 2/3 of the tongue Damage to the facial nerve - Extracranial lesions Paralysis or severe weakness of the muscles of facial expression Various causes Parotid gland pathology – e.g a tumour, parotitis, surgery. Infection of the nerve – particularly by the herpes virus Local anaesthetic (rare) Parotid gland tumour and surgery Summary Motor supply to muscles of facial expression Minor sensory role Taste to anterior two-thirds of tongue Parasympathetic innervation to: submandibular and sublingual salivary glands nasal, palatine and pharyngeal mucous glands lacrimal glands https://app.sli.do/event/eonQVofQQwcE41KTzieRzC References https://teachmeanatomy.info/head/cranial-nerves/facial-nerve/ https://www.anatomy.tv/titles https://aclandanatomy.com/ Norton, N.S. and Netter, F.H. (2017) Netter's head and neck anatomy for Dentistry. Elsevier (Chapter 5) Liebgott, B. (2018) The anatomical basis of Dentistry. PHILADELPHIA (U.A.): SAUNDERS.