ext & middle ear anatomy.pptx ear normal

Anatomy

1. ANATOMY OF EXTERNAL & MIDDLE EAR

2. ANATOMY OF EXTERNAL EAR El a stic carti la ge Helix Antihelix Tri a ngul a r foss a Sc a phoid foss a Conch a Cymba concha Incisura terminalis

3. SURGICAL IMPORTANCE CoJiloge from trogus, perichondrium from trogus or concho ond fat from eor lobule used for reconstructive middle eor surgeries Conchol cortiloge used to correct depressed nosol bridge

4. MIDDLE EAR CLEFT EUSTACHIAN TUBE MIDDLE EAR CAVITY (TYMPANIC CAVITY) ADITUS MASTOID ANTRUM MASTOID AIR CELLS

5. Development of Middle Ear Develops between the third and seventh months of intrauterine life Middle ear cleft – 1 st & partly from 2 nd arch Tympanic membrane- all three germinal layers Ossicles - malleus & incus – mesoderm of first arch Stapes- 2 nd arch except foot plate and annular ligament – Otic capsule

6. DEVELOPMENT OF TYMPANIC MEMBRANE Outer squamous layer = Ectoderm Middle fibrous layer = Mesoderm Inner mucous layer = Endoderm DEVELOPMENT OF EUSTACHIAN TUBE TUBOTYMPANIC RECESS

7. DEVELOPMENT OF THE OSSICLES Malleus and incus First pharyngeal arch cartilage (Meckel’s cartilage) Suprastructure of stapes Second pharyngeal arch cartilage (Reichert’s cartilage) Foot plate of stapes otic capsule

8. EPITHELIAL LINING EPITYMPANUM- flat , non ciliated cuboidal MESO & HYPOTYMPANUM- Pseudostratified ciliated columnar epithelium Mastoid- cuboidal epithelium

9. Anatomy of middle ear cleft Eustachian Tube Middle ear Aditus Antrum Air cells

10. Middle ear is a six sided cavity situated between the external ear laterally and the inner ear medially Divided into three compartments 1. Epitympanum or Attic 2. Mesotympanum 3. Hypotympanum Protympanum - middle ear around Eustachian tube orifice

11. BOUNDARIES OF THE MIDDLE EAR CAVITY Roof Floor Medial wall Lateral wall Anterior wall Posterior wall

12. ROOF OF MIDDLE EAR Tegmen tympani - Separates the middle ear cavity from middle cranial fossa Formed by petrous and squamous parts of temporal bone Petro squamous suture line Tegmen antri - roof of aditus & antrum

13. FLOOR OF THE MIDDLE EAR Formed by compact or pneumatised bone that separates the middle ear cavity from the jugular bulb Occasionally deficient Opening for tympanic branch of glossopharyngeal nerve (Jacobson’s Nerve)

14. LATERAL WALL OF MIDDLE EAR Upper part – Bony lateral wall of epitympanum Middle Part – Tympanic Membrane Lower Part – Bony Lateral wall of Hypotympanum

15. ANTERIOR WALL OF MIDDLE EAR Eustachian tube opening Canal for Tensor tympani muscle Separates the hypotympanum from internal carotid artery

16. MEDIAL WALL OF MIDDLE EAR Promontory Oval Window (Fenestra Vestibuli) Round Window (Fenestra cochlea) Subiculum Ponticulus Facial nerve canal (Fallopian canal)

17. POSTERIOR WALL OF MIDDLE EAR Aditus Fossa incudis Pyramidal Process Facial Recess Sinus Tympani

18. CONTENTS OF MIDDLE EAR Ossicles - Malleus Incus Stapes Muscles - Tensor Tympani Stapedius Nerves - Chorda Tympani Tympanic Plexus Mucosa

19. MALLEUS Head Neck Anterior Process Lateral Process Handle (Manubrium)

20. INCUS Body Short process Long process Lenticular process (Sometimes called fourth ossicle)

21. STAPES Head Neck Anterior Crus Posterior Crus Foot Plate

22. MUSCLES Tensor Tympani _first arch –V Stapedius - second arch – VII NERVES Chorda Tympani Tympanic Plexus

23. PRUSSAK’S SPACE Bounded by Lateral malleular fold Pars flaccida Neck of malleus Mucosal folds connected to the malleus Anterior malleolar fold (Anterior fold of von Troltsch) Posterior malleolar fold (Posterior fold of Von Troltsch) Superior malleolar fold

24. Blood Supply Anterior tympanic branch of maxillary artery Stylomastoid branch of posterior auricular artery Superior tympanic branch & petrosal branch of middle meningeal artery Tympanic branches from internal carotid artery Pterygoid canal branch

25. Venous Drainage Pterygoid venous plexus Superior petrosal sinus Lymphatic Drainage Upper deep cervical lymph nodes Nerve Supply Tympanic Plexus

26. MASTOID ANTRUM Air filled space in the petrous part of temporal bone Relations Superior - Middle cranial fossa Inferior - Jugular bulb Posterior Belly of Digastric Medial - Posterior Semicircular Canal Posterior cranial fossa Lateral - Post Auricular Skin Anterior - Middle Ear cavity Posterior - Sigmoid Sinus

27. MAC EWEN’S TRIANGLE Surgical landmark for mastoid antrum Boundaries Above – Supra mastoid crest In front – Posterosuperior margin of External auditory canal Tangetial line cutting the posterior meatal wall and suprameatal crest Mastoid antrum lies 1.5 cm deep to Mac Ewen’s triangle

28. MASTOID AIR CELL SYSTEMS Zygomatic Marginal Tegmen Squamous Tip cell Perisinus Perilabyrinthine Retrofacial cells Peritubal

29. PNEUMATISATION Well pneumatised / cellular Diploetic Sclerotic/ acellular Korner’s septum- persistent petrosquamous line

30. SURGICAL LANDMARKS FOR INDENTIFICATION OF FACIAL NERVE IN MIDDLE EAR Processus Cochleariformis – Curved ridge of bone which marks the anterior part of fallopian canal in the medial wall of middle ear Oval window – Facial nerve passes above the oval window Lateral semicircular canal – Lies posterosuperior to second genu of facial nerve

31. SURGICAL LANDMARKS FOR INDENTIFICATION OF FACIAL NERVE IN MIDDLE EAR (CONTINUED) COG – Bony ridge which hangs down from the tegmen tympani. Helps in the identification of first genu of facial nerve PYRAMID – Vertical segment of facial nerve lies 1-2 cm behind the pyramid.

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