Anatomy of External and Middle ear. Dr Sai Manohar 1
Human Ear For Anatomical description, Ear is divided into Auricle (or pinna) The external auditory canal The Middle Ear and its derivatives The Inner Ear. EXT Ear 2
Auricle 3
Auricle Single piece of Yellow elastic cartilage covered by skin. Incisura terminalis no cartilage b/w tragus & crus of helix endaural approach Several graft materials tragus, concha. 4
Nerve Supply Auricle 5
External Auditory Canal Bottom of concha TM 24mm. Outer part upwards, backwards & medially, Inner downwards, forwards & medially. To see TM pull pinna upwards, backwards & laterally. 6
Cartilaginous part Outer 1/3 rd 8mm continous with cartilage of pinna Fissures of Santorini parotid infections appear in meatus or vice cersa. Skin thick, ceruminous & pilosebaceous glands secrete wax. Hair confined to outer canal furuncles. 7
Bony part inner 2/3 rd 16mm. Skin thin, continuous over TM, devoid of glands & hair follicles 6mm lateral to TM narrowing - Isthmus. Ateroinferior part of deep meatus Anterior Recess Foramen of Huschke Anteroinferior in children infection to & fro from Parotid. 8
Relations of External Auditory Canal Superiorly middle cranial fossa. Posteriorly mastoid air cells & FN Inferiorly parotid gland. Anteriorly temporomandibular joint. Posterosuperior part of deep meatus related to mastoid antrum mastoiditis sagging. 9
Relations of External auditory canal 10
External Auditory Canal Nerve Supply Anterior wall & roof auriculotemporal N V3 Posterior wall & floor auricular branch of vagus X Arnolds N. Posterior wall sensory fibres of VII. 11
Tympanic Membrane 12
Tympanic Membrane Partition b/w EAC & ME. Oblique posterosuperior part is more lateral. 9-10mm tall, 8-9mm wide & 0.1mm thick. Pars Flaccida(Sharpnell s membrane) above lateral process of malleus & b/w notch of rivinus and anterior & posterior malleal folds. Not so taught, slightly pinkish. 13
Tympanic Membrane Pars Tensa - most of TM. Periphery thickened fibrocartilaginous ring Annulus Tympanicus. Central part tented inwards at tip of HOM Umbo. Cone of light tip of HOM to periphery in AI Quad. 14
Tympanic Membrane Three layers Outer epithelial layer Inner mucosal layer. Middle fibrous layer radial, circular & parabolic fibers. 15
Tympanic Membrane Nerve supply External surface of membrane corresponds to that of the meatus. Posterior half- Auricular branch of Xth cranial nerve Anterior half- Auriculotemporal branch of the Vth cranial nerve Medial surface Tympanic branch of CN IX Jacobson s N. 16
Middle Ear Cleft Vertical air containing cleft in the temporal bone Includes auditory tube, tympanic cavity & mastoid antrum and air cells. Lined by mucous membrane & filled with air. 17
Middle Ear Cross section of ear including the middle ear 18
Middle Ear Mesotympanum level of PT Epitympanum Attic above PT Hypotympanum below PT Six sided box. Roof thin plate of bone Tegmen Tympani also roof of aditus & antrum separates ME from middle cranial fossa. 19
Middle Ear The Floor thin plate of bone separates ME from Jugular bulb. sometimes deficient. The Anterior Wall thin plate of bone separates ME from Carotid artery. 2 openings lower ET, Upper canal for Tensor tympani. 20
The Posterior Wall Middle Ear Aditus Attic communicates with Antrum. bony projection Pyramid tendon of stapedius. FN runs behind pyramid. Facial recess FN, Chorda tympani, Fossa incudis. The Lateral Wall TM Bony outer Attic Wall Scutum. 21
Posterior wall of tympanic cavity 22
Middle Ear The Medial Wall By Labyrinth Bulge Promontory Basal coil of Cochlea Oval Window Foot plate of Stapes. Round Window Secondary TM. Canal for facial N. Prominance of lateral SCCanal. Processus cochleariformis Sinus tympani deep recess medial to pyramid Subiculum below & Ponticulus above. 23
Medial wall of Tympanic cavity 24
Mastoid Antrum Large air containing space in upper part of Mastoid, communicating with Attic through Aditus. Roof Tegmen antri Middle cranial fossa. Lateral wall plate of bone 1.5cm thick marked externally by suprameatal (Mac Ewen s) Triangle. 25
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Aditus ad Antrum Attic communicates with Antrum. Prominance of Horizontal SCCon its medial side. Fossa incudis laterally. 27
Mastoid & its Air Cell System Mastoid bone cortex with a honeycomb of air cells underneath. Depending on air cell development Well pneumatised / cellular Diploetic marrow spaces & few air cells. Sclerotic / acellular 28
Mastoid Air Cell System Depending on location Zygomatic cells. - squamous cells Tegmen cells. Perisinus cells. Retrofacial cells. Perilabyrinthine cells. Peritubal cells. Tip cells 29
Development of Mastoid From Squamous & Petrous bones. Petrosquamal suture may persist as a bony plate Korner s Septum - Superficial squamous cells from deep petrous cells. Difficulty in locating antrum & deeper cells. 30
Contents of Middle Ear Chain of 3 small movable bones, 2 muscles, the chorda tympani and the tympanic plexus of nerves. Malleus 31
Ossicles The Malleus head, neck, handle, a lateral & an anterior process. Head & neck in Attic. Handle in fibrous layer of TM. Lateral process attachment to anterior & posterior malleal folds. 32
The Incus a body & a short process in attic, & a long process attaches to head of stapes. The Stapes head, neck, anterior & posterior crura & a footplate oval window. 33
Middle Ear Incus Stapes 34
Auditory Muscles Middle Ear Tensor Tympani - to neck of malleus tenses TM branch of mandibular N. Stapedius to neck of stapes dampen loud sounds Facial N 35
Chorda tympani N - Branch of FN enters ME through posterior canaliculus, runs on medial surface of TM b/w handle of malleus & long process of incus. Taste from anterior 2/3 rd of tongue, secretomotor to submandibular & sublingual glands. 36
Tympanic plexus On promontory & formed by 1.Tympanic branch of Glossopharyngeal nerve 2. sympathetic fibers from plexus of internal carotid artery Tympanic plexus supplies Lining membrane of tympanic cavity, mastoid air cells and auditory tube. The lesser superficial petrosal nerve otic ganglion auriculotemporal nerve - secretomotor to Parotid. 37
Lining of ME Cleft Mucous membrane of Nasopharynx is continuous with that of ME, Aditus, Antrum & air cells. Wraps ME structures Histologically ET ciliated pseudostratified columnar in cartilaginous part & columnar in bony part, mucus glands in submucosa Tympanic cavity ciliated clomnar in anterior & inferior parts, cuboidal inposterior part. Epitympanum & mastoid- flat nonciliated epithelium 38
Blood supply of ME Anterior tympanic branch of maxillary artery. Stylomastoid branch of posterior auricular artery. Petrosal branch of middle meningeal artery. Superior tympanic branch of middle meningeal artery. Branch of artery of pterygoid canal. Tympanic branch of internal carotid. 39
Lymphatic drainage ME retropharyngeal & parotid nodes. ET retropharyngeal nodes. 40
THANK YOU 41