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Similar to Middle ear cavity(with handmade illustrations)
Middle ear cavity(with handmade illustrations)
- 1. Middle ear Dr. Manukrishnan.K
- 2. Tympanic cavity/tympanum • Narrowair filled space situated in the petrous part of the temporal bone b/w external ear & internal ear. • Resembles a six sided box ( like a match box) Dr.Manu krishnan.K 2
- 3. Dimensions/measurements Vertically & Anterio posteriorly •15mm Transverse diameter - • 6mm above • 4mm below • 2mm oppo.to umbo Dr.Manu krishnan.K 3
- 4. PARTS • Tympanic cavityproper – opposite to the Tympanic membrane • Epitympanic recess (attic)– above the level of Tympanic membrane(TM) Dr.Manu krishnan.K 4
- 5. Middle ear cavityis further divided : Portion of middle ear lies 1. Epitympanum-above the level of TM 2. Mesotympanum –at the level opposite to TM 3. Hypotympanum-below the level of TM 4. Protympanum- around the eustachian tube opening Dr.Manu krishnan.K 5
- 6. Dr.Manu krishnan.K 6 CORONALSECTION THROUGH MIDDLE EAR CAVITY
- 7. PARTS 1. MALLEUS 2. TYMPANICMEMBRANE 3. EPITYMPANUM 4. INCUS 5. STAPES 6. OVAL WINDOW 7. MESOTYMPANUM 8. HYPOTYMPANUM Dr.Manu krishnan.K 7
- 8. COMMUNICATIONS & CONTENTS COMMUNICATIONS •Anteriorly-nasopharynx with eustachian tube • Posteriorly –mastoid antrum &mastoid air cells CONTENTS • 3 small bones-Malleus, Incus, Stapes(ear ossicles) • Ligment of ear ossicles • Tensor tympani & stapedius muscle • Vessels supplying & draining the middle ear • Nerves –Chorda tympani & tympanic plexus Dr.Manu krishnan.K 8
- 9. WALLS OF MIDDLEEAR CAVITY Six walls: 1. Roof/tegmental wall 2. Floor/jugular wall 3. Anterior wall/carotid wall 4. Posterior/mastoid wall 5. Lateral/membran ous wall 6. Medial/labrynthi ne wall Dr.Manu krishnan.K 9
- 10. The Roof/ Tegmentalwall • Separates the middle ear from the middle cranial fossa • Formed by thin plate of bone called Tegmen tympani. • Plate is prolonged backwards as the roof of the canal for the tensor tympani. • Pierced by greater and lesser petrosal nerves. Dr.Manu krishnan.K 10
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- 12. Floor / jugularWall • Formed by thin plate of bone • separates middle ear from the superior bulb of the internal jugular vein. • Aperture for Jacobson nerve Dr.Manu krishnan.K 12
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- 14. Anterior / carotidWall • Narrow ,separates middle ear from internal carotid artery. • Upper part - the opening of the canal for the tensor tympani and opening of auditory tube • lower part- superior & Inferior carotico tympanic vessels &nerves Dr.Manu krishnan.K 14
- 15. Posterior/mastoid wall • Superiorly-aditusthrough which epitympanic recess communicate with the mastoid antrum. • Fossa incudis-depression which lodges the short process of the incus • Pyramid-a conical projection ,opening at the apex for the passage of tendon of stapedius muscle • Posterior canaliculus-for the chorda tympani Dr.Manu krishnan.K 15
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- 17. Lateral / Membranouswall Separates middle ear from External auditory meatus Formed by • Tympanic membrane • Tympanic ring & sulcus • Partially by squamous temporal bone Apertures • Petro tympanic fissure-upper end of the bony rim • Anterior canaliculus-for chorda tymapani nerve Dr.Manu krishnan.K 17
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- 19. Medial wall /labryinthine wall Separates middle ear from inner ear Promontory –rounded bulging produced by basal turn of cochlea Fenestra vestibuli (Oval window) -Oval opening posterio superior to promontory -Measures 3.25x1.75mm Fenestra cochlea(round window) - Lies postero inferior to promontory -Opens into floor scala tympani -Measures 1.5x1.3mm Dr.Manu krishnan.K 19
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- 21. Blood supply Arterial supply •Anterior tympanic branch of maxillary artery • Super.Tympanic branch of middle meningeal artery • branch of internal carotid artery • Petrosal branch of middle meningeal artery. Venous drainage • Superior petrosal sinus & pterigoid plexus Dr.Manu krishnan.K 21
- 22. Nerve supply • Tympanicbranch of glossopharyngeal nerve • Superior & inferior Carotico tympanic nerves Dr.Manu krishnan.K 22