Ear Anatomy

Ear Anatomy describe all the part of ear such as outer ear,Middle ear ,and Inner ear.
it was presented by Dr Ndayisaba Corneille

1. ANATOMY OF THE EAR by DR NDAYISABA CORNEILLE INTERNATIONAL HEALTH SCIENCE UNIVERSITY

2. THREE MAJOR DIVISION OF EAR 1/26/2019 Dr Ndayisaba Corneille

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4. OUTER EAR Its functions Collects sound Localization Resonator Protection Sensitive (earlobe) It has Three main parts: Pinna(auricle) , External Auditory Meatus and eardrum(tympanic mebrane ) 1/26/2019 Dr Ndayisaba Corneille

5. Pinna(auricle) T he visible portion that is commonly referred to as "the ear" , It consists of cartilege and skin H elps localize sound sources and directs them towards the external auditory meatus and on to the tympanic membrane Lymphatics ;drain into parotid group,upper deep cervical and mastoid lymphnodes Veins ;dain into into external jugular,common facial vein Arteries ;posterior auricular branch of external carotid artery,ant.auricular branch of superficial temporal and a branch of occipital artery 1/26/2019 Dr Ndayisaba Corneille

6. Auriculotemporal nerve (CN V3 ): It is a branch of mandibular division of trigeminal nerve and supplies anterosuperior part of lateral surface of pinna including tragusand crus of helix. CN VII (facial nerve) : It innervates the skin of lateral concha and antihelix, lobule and mastoid. CN X ( vagus nerve) : Its auricular branch (Arnold’s nerve) supplies to concha and post auricular skin. Greater auricular nerve (C2,3): This nerve of cervical plexus supplies most of the medial surface of auricle and posterior part of lateral surface and the postauricular region. Lesser occipital nerve (C2): This nerve of cervical plexus supplies upper part of medial surface of auricle and postauricular region. Nerve supply 1/26/2019 Dr Ndayisaba Corneille

7. Is a curved tube about 2.5cm that lies in the temporal bone and leads from the auricle to the eardrum (tympanic memb ) Near to the exterior of its opening there is a few hairs and specialized sebaceous(oil)glands called ceruminous glands that secrete cerumen (earwax ) The combination of hairs and cerumen help prevent dust and foreign objects from entering the ear and cleaning mechanism of ear NERVE SUPLY ( i) Anterior wall and roof : auriculotemporal (V3 ) supplies anterosuperior wall of external auditory canal (ii) Posterior wall and floor : auricular branch of vagus nerve(CNX) supplies to inferoposterior external auditory canal . Posterior wall of the auditory canal also receives sensory fibres of cranial N VII (facial nerve ) through auricular branch of vagus . External Auditory Meatus 1/26/2019 Dr Ndayisaba Corneille

8. Eardrum(tympanic membrane ) I t is a thin,semitransparent partiton between the external auditory canal and middle ear. It has two parts : ( a) Pars Tensa : I t forms most of tympanic membrane.. I ts periphery is thickened to form a fibro cartilaginous ring called the annulus tympanicus which fits in the tympanic sulcus. The central part is tented inwards at the level of the tip of malleus and is called the umbo . (b) Pars Flaccida (Shrapnel's Membrane) This is situated above the lateral process of malleus between the notch of Rivinus and the anterior and posterior malleolar folds. It has three layers: (i) Outer epithelial layer , which is continuous with the skin lining the meatus. no hairs and glands (ii) Middle fibrous layer , which encloses the handle of malleus and has three types of fibres-the radial, circular and the parabolic. (iii) Inner mucosal layer , which is continuous with the mucosa of the middle ear 1/26/2019 Dr Ndayisaba Corneille

9. Malleus 2,6 Anterior mallear fold Post mallear fold Pars flaccida projection of long process of incus. Pars tensa Annular ligament. Tympanic membrane NERVE SUPPLY (i) Anterior half of lateral surface: auriculotemporal (V 3) (ii) Posterior half of lateral surface: auricular branch of vagus nerve (CN X ) (Arnold’s nerve ) (iii) Medial surface: Tympanic branch of CN IX glossopharyngeal nerve (Jacobson's nerve). 1/26/2019 Dr Ndayisaba Corneille

10. MIDDLE EAR It has two main parts: Auditory ossicles (transmit and mplify sound from the tympanic membrane to the oval window) A uditory( eustachian )tube (equalizes pressure on both sides of the tympanic membrane 1/26/2019 Dr Ndayisaba Corneille

11. MIDDLE EAR The middle ear together with the Eustachian tube, aditus,antrum and mastoid air cells is called the middle ear cleft . its lined with mucous membrane and filled with air. Aditus and Antrum : Aditus is an opening through which the attic communicates with the antrum . The Mastoid and its Air Cell System: The mastoid consists of bone cortex with a "honeycomb “ of air cells underneath. Depending on development of air cell, three types of mastoid have been described: Well-pneumatised or cellular; Diploetic ; Sclerotic or acellular It is divided into: Mesotympanum (lying opposite to parsa tensa ). Epitmpanum or attic( lying above parsa tensa but medial to shrapnell ’ s membrane and the bony lateral attic wall) Hypotympanum ( lying below the level of parca tensa ). 1/26/2019 Dr Ndayisaba Corneille

12. Middle ear cleft 1/26/2019 Dr Ndayisaba Corneille

13. BOUNDARIES OF MIDDLE EAR Roof ( Tegmental wall ): is formed by a thin plate of bone called tegmen tympani. Floor ( Jugular wall ) : is also thin plate of bone which separates tympanic cavity from the jagular bulb Anterior ( Carotid wall ) : has a thin plate of bone which separates the cavity from internal carotid artery . has following features : Eustachian tube, Canal of tensor tympani muscle, Canal for chorda tympani nerve, Attachment of anterior malleolar ligament Posterior ( Mastoid wall ) : lies close to the mastoid air cells . Has: Pyramid, Aditus ad antrum, Facial nerve Medial ( Labyrinthine wall ) : is formed by labyrinth( including promontory, Round window, oval window.) Lateral wall : is formed largely by tympanic membrane . 1/26/2019 Dr Ndayisaba Corneille

14. Auditory ossicles – Malleus • Attaches to ear drum • Articulates with incus – Incus • Articulates with stapes – Stapes (stirrup) • Footplate of stapes fits into oval window Ossicles Allows communication btn the external and internal ear and amplification 1/26/2019 Dr Ndayisaba Corneille

15. MIDDLE EAR MUSCLES There are two middle ear muscles also called intratympanic muscle : tensor tympani and the stapedius . 1 . Tensor tympani : It runs above the eustachian tube . Originate from Bony tunnel above the osseous part of eustachian tube.inserted Just below the neck of malleus and is supplied by a branch of mandibular division of trigeminal nerve (CN V3) 2 . Stapedius : On contraction it reduces the loud sounds and prevents noise trauma to the inner ear. Originate from Conical cavity and canal within pyramid.it insert to the neck stapes and supplied by a branch of CN VII (nerve to stapedius of facial nerve). 1/26/2019 Dr Ndayisaba Corneille

16. A uditory( eustachian )tube It consists of both of both bone and hyaline cartilage and connects the middle ear with the nasopharynx.it is normally closed at its medial(pharyngeal) end;during swallowing and yawning,it opens,then atmospheric pressure from throat enters or leaves the middle ear until int.pressure is =to external pressure. When the pressures are balanced,the eardrum vibrates freely as soundwaves strike it It is also a route where pathogens can travel from throat and nose to the middle ear 1/26/2019 Dr Ndayisaba Corneille

17. NERVE SUPPLY : tympanic plexus which is formed by 1) tympanic branch of glossopharngeal nerve and 2) sympathetic fibers from the plexus round the internal carotid artery. Tympanic plexus supplies innervation to the medial surface of the tympanic membrane, tympanic cavity, mastoid air cells and the bony Eustachian tube. It also carries secretomotor fibres for the parotid gland. Chorda Tympani Nerve: It is a branch of the facial nerve which enters the middle ear through posterior canaliculus , and runs on the medial surface of the tympanic membrane between the handle of malleus and long process of incus, above the attachment of tendon of tensor tympani. It carries taste from anterior two-thirds of tongue and supplies secretomotor fibres to the submaxi llary and su blingual sa livary glands 1/26/2019 Dr Ndayisaba Corneille

18. Blood supply : Middle ear is supplied by six arteries, out of which two are the main, i.e. (i) Anterior tympanic branch of maxillary artery which supplies tympanic membrane. (ii) Stylomastoid branch of posterior auricular artery which supplies middle ear and mastoid air cells venous Drainage Veins from the middle ear cleft drain into pterygoid venous plexus , superior petrosal sinus and sigmoid sinus Lymphatic drainage of ear The lymphatics of middle ear drain into retropharyngeal and parotid nodes. Eustachian tube lymphatics drain into retropharyngeal group of lymph nodes . Internal ear does not have any lymphatics 1/26/2019 Dr Ndayisaba Corneille

19. SUMMARY Middle ear contains: Air Two muscles ( Tensor tympani and stapedius ) Two nerves( corda tympani and tympanic plexus on the promontory) 3 bone (maleus, incus, stapes) Mucosa of middle ear is stratified columnar with goblet and seromucinous glands Its function: Conduction Conduct sound from the outer ear to the inner ear Protection Creates a barrier that protects the middle and inner areas from foreign objects Middle ear muscles may provide protection from loud sounds Transducer Converts acoustic energy to mechanical energy Converts mechanical energy to hydraulic energy Amplifie r Transformer action of the middle ear only about 1/1000 of the acoustic energy in air would be transmitted to the inner-ear fluids (about 30 dB hearing loss) 1/26/2019 Dr Ndayisaba Corneille

20. INNER EAR The internal ear or the labyrinth is an important organ of hearing and balance . It consists of a bony and a membranous labyrinth . The membranous labyrinth is filled with a clear fluid called endolymph while the space between membranous and bony labyrinths is filled with perilymph . Bony labyrinth : It consists of the vestibule, the semicircular canals and the cochlea . Membranous labyrinth : consists of The membranous cochlear duct The membranous semicircular canals. The utricle and saccule (that lie within the vestibule) The endolymphatic duct and sac 1/26/2019 Dr Ndayisaba Corneille

21. Cochlear part it is fluid filled organ. it is bony coiled up on axis like a snail ’ s shell (central pyramid called modiolus ) Its basal turn forms the promontory . It has three compartment Scala vestibule scala tympani Above 2 are filled with perilymph and communicate with each other at apex of cochlea through Helicotrema c. scala media(cochlear duct): its blind coiled tube and it appears triangular on cross-section and its three wall are formed by: basilar membrane which supports the organ of corti ( inner, outer hair cells and tectorial mem ) The Reissner ’ s membrane which separate it from scala vestibuli , The stria vasculars which contains vascular epithelium and is concerned with secretion of endolymph . 1/26/2019 Dr Ndayisaba Corneille

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23. B) Vestibular part: - its bony cavity that lodges the utricle and saccule . - it contains the sensory organs responsible for equilibrium ( responsible for linear acceleration) C) Semicircular canals(SCC): they are not complete circles, the have one ampulary and one non- ampulary ends. Oriented as superior, lateral, posterior canals with 90 degree relation to each other. Sensory organs are crista ampularis ( which is responsible for angular acceleration). the vestibular nerve: Superior and inferior vestibular nerve arise from the sensory organs of SCC and utricle and saccule to enter the internal acoustic canal. 1/26/2019 Dr Ndayisaba Corneille

24. Membranous labyrinth Cochlear Duct (Membranous Cochlea or Scala Media) This blind coiled tube, which appears triangular on cross section , is connected to the saccule through ductus reunions Saccule : The saccule lies anterior to the utricle opposite the stapes footplate in the bony vestibule. Its sensory epithelium, macula responds to linear acceleration and deceleration . The saccule is connected to the cochlea through the thin reunion duct Semicircular Ducts : The three semicircular ducts, which open in the utricle, correspond exactly to the three bony canals Endolymphatic Duct and Sac : The ducts from utricle and saccule unite and form utriculo saccular duct, which continues as endolymphatic duct that passes through thevestibular aqueduct Endolymphatic sac is thought to regulate pressure of membranous labyrinth. 1/26/2019 Dr Ndayisaba Corneille

25. INNER EAR FLUIDS Perilymph fills the space between bony and membranous labyrinth while endolymph fills the entire membranous labyrinth P erilymph It resembles extracellular fluid and is rich in sodium ions Originate from Filtrate of blood serum from the capillaries of spiral ligament and CSF reaching labyrinth via aqueduct of cochlea. E ndolymph It resembles intracellular fluid and is rich in potassium ions Protein and glucose contents are less than in perilymph. „ originate from Stria vascularis and Dark cells of utricle and ampullated ends of semicircular ducts . 1/26/2019 Dr Ndayisaba Corneille

26. This sensory organ of the hearing, is situated on the basilar membrane. It is spread like a ribbon along the entire length of basilar membrane. It consists of: 1 . Tunnel of Corti : This tunnel, which is situated between the inner and outer rods, contains a fluid called cortilymph . The functions of the rods and cortilymph are yet not clear. 2 . Hair Cells : hese important receptor cells of hearing transduce sound energy into electrical energy. There are two types of hair cells—inner and outer. ORGAN OF CORTI 1/26/2019 Dr Ndayisaba Corneille

27. REFERENCE 1,Harold Ludman and Patrick J Bradley 2007 Ear , Nose and Throat Fifth Edition 2,Mohan Bansal 2013 Diseases of Ear, Nose and Throat First edition published by jaypee brothers medical ;New Delhi in India 3, Ghada M W F. Ear Anatomy . Glob J Otolaryngol 2017 1/26/2019 Dr Ndayisaba Corneille

28. THANK FOR YOUR ATTENTION 1/26/2019 Dr Ndayisaba Corneille