ANATOMY OF MIDDLE EAR BY DINESH V.pptx

Dinesh

1. ANATOMY OF THE MIDDLE EAR BY : DINESH V

2.  Contents of middle ear  Walls of middle ear  Mastoid antrum  The mastoid and its air cell system  Developement of mastoid  Blood supply of middle ear Overview

3. MIDDLE EAR : The middle ear together with the eustachian tube, aditus antrum and mastoid air cells is called middle ear cleft it is lined by mucous membrane and filled with air.

4. COMMUNICATION The middle ear communicates: Anteriorly with nasopharynx through pharyngotympanic tube. Posteriorly with mastoid antrum and mastoid air cells through aditus to antrum called aditus ad antrum.

5. PARTS OF TYMPANIC CAVITY : MESOTYMPANUM EPITYMPANUM HYPOTYMPANUM

6. The E ustachian tube , tympanic cavity , A ttic, M astoid air cells develop from the E ndoderm of T ubotympanic recess which arises from the F irst P haryngeal P ouches .

7. Malleus and I ncus are derived from M esoderm of the F irst A rch while the S tapes develop from the S econd A rch except its footplate and annular ligament which are derived from the ottic capsule .

8. CONTENTS Three small bones called ear ossicles : malleus, incus, and stapes. Two muscles: tensor tympani and stapedius. Two nerves: chorda tympani and tympanic plexus. Vessels supplying and draining the middle ear. Ligaments of the ear ossicles .

9. INTRA TYMPANIC MUSCLE TENSOR TYMPANI: MANDIBULAR NERVE STAPEDIUS: FACIAL NERVE

10. IT LIES ON PROMONTORY WHICH IS FORMED BY 1.TYMPANIC BRANCH OF GLOSSOPHARNGEAL NERVE 2. SYMPATHETIC FIBRES FROM THE PLEXUS ROUND THE ICA
IT CARRIES SECRETOMOTOR FIBRES FOR THE PAROTID GLAND AND IT HAS CLINICAL CORRELATION :FREYS SYNDROME TYMPANIC PLEXUS

11. CHODRA TYMPANI NERVE BRANCH OF FACIAL NERVE
ENTER INTO MIDDLE EAR THROUGH POSTERIOR CANALICULUS
IT CARRIES TASTE SENSE FROM 2/3 OF TONGUE
IT SUPPLIES SECRETOMOTOR FIBRES TO SUBMAXILLARY AND SUBLINGUAL GLANDS

12. Boundaries ROOF: FORMED BY TEGMEN TYMPANI (THIN PLATE OF BONE ) SEPARATES TYMPANIC CAVITY FROM THE MIDDLE CRANIAL FOSSA

13. FLOOR: ALSO MADE OF THIN PLATE OF BONE SEPEARATES TYMPANIC CAVITY FROM JUGULAR BULB

14. ANTERIOR WALL: SEPERATES CAVITY FROM INTERNAL CAROTID ARTERY TWO OPENING 1. CANAL OF TENSOR TYMPANI MUSCLE 2. EUSTACHIAN TUBE OPENING

15. POSTERIOR WALL: The posterior wall lies close to the mastoid air cells. It presents a bony projection called pyramid which gives orgin to stapedius muscle Facial nerve runs in facial canal. Chorda tympani a branch of facial nerve, leaves emerges from facial canal through posterior canaliculus.

16. MEDIAL WALL: PROMONTORY OVAL WINDOW IS CLOSED BY FOOTPLATE OF STAPES ROUND WINDOW IS CLOSED BY SECONDARY TYMPANIC MEMBRANE CANAL FOR FACIAL NERVE PRESENT ABOVE THE OVAL WINDOW BONY LATERAL SEMICIRCULAR CANAL PROCESSUS COCHLEARIFORMIS

17. LATERAL WALL : FORMED LARGELY BY THE TYMPANIC MEMBRANE SEMI TRANSPARENT MEMBRANE WHICH FORMS WINDOW OF MIDDLE EAR

18. MASTOID ANTRUM It is a large air-containing space in the upper part of the mastoid process. It communicates anteriorly with tympanic cavity through aditus ad antrum. Its roof is formed by tegmen antri , which is the backward continuation of tegmen tympani. It separates the antrum from middle cranial fossa.

19. MASTOID AND ITS AIR SYSTEM: Depending on developing of air cells Mastoid is of following types 1.Well-pneumatized or cellular.-Mastoid cells are well-developed and intervening septa are thin. 2. Diploetic -Mastoid consists of marrow spaces and a few air cells. 3. Sclerotic or acellular .-There are no cells or marrow spaces .

20. DEVELOPMENT OF MASTOID Mastoid develops from the squamous and petrous bones. The petrosquamosal suture may persist as a bony plate. The Korner’s septum, separating superficial squamosal cells from the deep petrosal cells.

21. BLOOD SUPPLY OF MIDDLE EAR : 6ARTERIES: 2 MAIN; ANTERIOR TYMPANIC BRANCH OF MAXILLARY ARTERY – TYMPANIC MEMBRANE STYLOMASTOID BRANCH OF POSTERIOR AURICULAR ARTERY –MIDDLE EAR AND MASTOID AIR CELLS 4 MINOR PETROSAL BRANCH OF MMA SUPERIOR TYMPANIC BRANCH OF MMA BRANCH OF ARTERY OF PTEYGOID CANAL TYMPANIC BRANCH OF ICA

22. VENOUS AND LYMPHATIC DRAINAGE : VEINS DRAIN INTO PTERYGOID VENOUS PLEXUS AND SUPERIOR PETROSAL SINUS RETROPHARYNGEAL NODES PAROTID LYMPH NODES UPPER DEEP CERVICAL LYMPH NODES

23. Clinical aspects Mastoidits : infection of Mastoid process or the large bone behind your ear . Middle ear infection cause most cases of mastoiditis Facial nerve palsy: during surgical procedure which involve middle ear accidental damage to facial nerve may be caused which leads to facial muscles paralysis and sometimes loss of taste.

24. SOURCE BOOK- DISEASES OF EAR NOSE THROAT BY DHINGRA TEXT BOOK OF ANATOMY BY VISHRAM SINGH

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