MIDDLE EAR ANATOMY OTORHINOLARYNGOLOGY.pptx

Anatomy of Middle Ear

1. MIDDLE EAR ANATOMY

2. Features Also called – The Tympanic cavity or Tympanum It is a narrow air filled space. Site – Petrous part of the temporal bone between the external ear and internal ear.

3. Middle ear cavity Parts : Epitympanum/attic - widest or largest Mesotympanum - narrowest Hypotympanum - smallest Contents: Three Ear Ossicles – malleus; incus and the stapes Two Muscles – the tensor tympani and the stapedius Nerves – chorda tympani and tympanic plexus Vessels supplying and draining middle ear

4. Middle Ear Cavity

5. Boundaries Middle ear is a cube like cavity with 6 boundaries: 1) Roof or Tegmental Wall 2) Floor or Jugular Wall 3) Anterior or Carotid Wall 4) Posterior or Mastoid Wall 5) Lateral or Membranous Wall 6) Medial or Labyrinthine Wall

6. Roof / tegmental wall Formed by – Tegmen Tympani Separates middle ear cavity from the middle cranial fossa.

7. Floor/jugular wall Formed by – thin plate of temporal bone Separates the middle ear from the superior bulb of the internal jugular vein. Tympanic canaliculus is present near the medial wall transmitting tympanic branch of glossopharyngeal nerve to the medial wall

8. Anterior/carotid wall Separates middle ear from the internal carotid artery present anteriorly to middle ear. It bears : -Opening of the canal for the tensor tympani - Canal of Huguier for exit of chorda tympani - Protympanum area consisting eustachian tube orifice

9. Posterior/mastoid wall Common wall between the middle ear and mastoid. It presents with: - Aditus : opening which connects epitympanum to the mastoid antrum -Vertical or mastoid segment of facial nerve -Fossa incudes - Pyramid - Posterior canaliculus for the Chorda tympani -Facial recess area and Sinus tympani area

10. Lateral/membranous wall Formed: - mainly by Tympanic membrane -partly by Scutum (a part of squamous temporal bone) in the region of epitympanic recess. Separates the middle ear from the external auditory canal .

11. Medial/labyrinthine wall Separates the middle ear from inner ear Structures present are: - Promontary - Fenestra vestibuli or oval window - Fenestra cochleae or round window - Prominence of lateral semicircular canal - Horizontal fallopian canal of facial nerve - Processus cochleariformis

12. Functions of the Middle Ear Transmission of sound waves Impedence matching – also known as transformer action Dampening of sound by stapedial reflex

13. CLINICAL ANATOMY OTOSCLEROSIS – fixation of footplate of stapes leading to conductive hearing loss HYPERACUSIS ACUTE OTITIS MEDIA – acute infection of middle ear most common route eustachian tube SEROUS OTITIS MEDIA CHRONIC SQUAMOUS OTITIS MEDIA

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