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Anatomy of Ear & Mastoid

Anatomy of Ear & Mastoid. Dr. Vishal Sharma. Embryology. Parts of ear. External ear:  Pinna / auricle  External auditory canal Middle ear cleft:  Eustachian tube  Tympanic cavity (middle ear)

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Anatomy of Ear & Mastoid

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  1. Anatomy of Ear & Mastoid Dr. Vishal Sharma

  2. Embryology

  3. Parts of ear External ear: Pinna / auricle  External auditory canal Middle ear cleft: Eustachian tube  Tympanic cavity (middle ear)  Mastoid air cell system Inner ear (labyrinth): Cochlea  Vestibule  Semicircular canals

  4. External Ear

  5. External auditory canal • 24 mm long; Lateral 1/3 Cartilaginous(8 mm): up + back + medial. Medial 2/3 Bony (16 mm): down + forward + medial. Pinna pulled up + back + lateral to straighten external auditory canal. • Only cartilaginous skin has hair follicles: furuncle • Cartilaginous fissure of Santorini & bony foramen of Huschke: passage of infection to and from parotid gland

  6. Nerve supply of E.A.C.

  7. Middle ear cleft Consists of: • Eustachian tube • Tympanic cavity (middle ear) • Aditus • Mastoid air cell system • Develops from tubo-tympanic recess

  8. Middle Ear

  9. Tympanic membrane • Pearly white semi-translucent membrane • Obliquely placed at 550 to floor • 2 parts: pars tensa and pars flaccida • 3 layers of pars tensa: outer epithelial, middle fibrous & inner mucosal • Fibrous layer disorganized in pars flaccida • Annulus deficient superiorly as notch of Rivinus

  10. Otoscopic view

  11. 1. Epitympanum: Bounded laterally by scutum + pars flaccida & medially by bone above tympanic part of facial nerve 2. Mesotympanum:Middle ear cavity lying opposite pars tensa & bony tympanic annulus 3. Hypotympanum: Middle ear cavity below level of bony tympanic annulus 4. Posterior tympanum:Middle ear cavity behind bony tympanic annulus 5. Anterior tympanum or Pro-tympanum: Middle ear cavity in front of bony tympanic annulus

  12. Walls of middle ear Roof:Tegmen tympani, middle cranial fossa Floor:Jugular bulb, carotid artery Anterior:Tensor tympani, ET orifice, carotid artery Posterior:Aditus, fossa incudis, pyramidal eminence, facial recess, sinus tympani Lateral:Tympanic membrane, scutum Medial:Promontory, oval window, round window, lateral SCC, facial nerve (tympanic part)

  13. Lateral wall • Membranous: a. Tympanic membrane • Bony a. Lateral attic wall above pars flaccida (Scutum) b. Lateral wall of hypotympanum

  14. Posterior wall • Aditus ad antrum • Fossa incudis for short process of incus • Bulge produced by lateral semicircular canal • Pyramidal eminence for stapedius tendon • Bulge produced by vertical part of facial nerve • Sinus tympani • Facial recess

  15. Sinus Tympani Boundaries: • Superior: Ponticulus • Inferior: Subiculum • Lateral: Mastoid Segment of Facial Nerve • Medial: Posterior semicircular canal It evades direct surgical visualization during surgery. Site for cholesteatoma recurrence

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