Anatomy & embryology ext ear & middle ear

12,888 views

Published on

0 Comments
26 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
12,888
On SlideShare
0
From Embeds
0
Number of Embeds
31
Actions
Shares
0
Downloads
790
Comments
0
Likes
26
Embeds 0
No embeds

No notes for slide

Anatomy & embryology ext ear & middle ear

  1. 1. ANATOMY & EMBRYOLOGY OF THE EXTERNAL & MIDDLE EAR Dr. Mohammed Shafeeq
  2. 2. EAR: ● External Ear ● Middle Ear ● Internal Ear (Labyrinth)
  3. 3. Embryology – External Ear ● develops around the first branchial arch
  4. 4. AURICLE: ● Around 6th week of IUL ● Developed from a series of small cartilaginous tubercles around 1st pharyngeal groove - 'Hillocks' or 'Tubercles of His'
  5. 5. ● First Pharyngeal Arch 1) Tragus ● Second Pharyngeal Arch 2) Crus of helix 3) Helix 4) Anti helix 5) Anti tragus 6) Ear lobule
  6. 6. ● Anomalies of Auricle (Pinna): 1) Preauricular sinus 2) Anotia 3) Bat ear deformity
  7. 7. EXTERNAL ACOUSTIC CANAL: ● ● ● ● Develops from surface ectoderm covering the dorsal end of 1st pharyngeal groove Meatus deepens by proliferation of its ectoderm Anteriorly placed bud of epithelial cells expand vertically to form the skin which will cover the future TM Clumps of cells then opens up as a slit to form the canal lumen and produce the pars tensa and deep external canal epithelium
  8. 8. ● Anomalies of EAC: 1) Atresia 2) Changes in curvature of canal 3) Stenosis
  9. 9. ● Tympanic Membrane: 1) Inner mucosal layer from ENDODERM 2) Middle fibrous layer from MESODERM 3) Outer epithelial layer from ECTODERM
  10. 10. MIDDLE EAR - Embryology ● st rd 1 pharyngeal develops by 3 week of IULof which, - proximal narrow part forms Eustachian Tube - distal dilated part forms tubotympanic recess, later to Middle Ear Cleft - in later fetal life, diverticulum appears from tubotympanic recess forming the Mastoid Antrum
  11. 11. ● OSSICLES: - Anson in 1959 - from 1st and 2nd arch cartilages - 1st arch (Meckel's) cartilage: head of malleus & body of incus - 2nd arch (Reichert's) cartilage: handle of malleus, long process of incus, crurae of stapes - Otic capsule: foot plate of Stapes
  12. 12. Middle Ear Spaces & Folds: numerous spaces and folds are formed when mucous membrane of tubotympanic recess encircle the ossicles. Attic Compartment: - Anterior Compartment - PosteriorCompartment Compartments of Mesotympanum: - Anterior Malleolar Fold - Posterior Malleolar Fold - Tensor Tympani Fold
  13. 13. ● Prussak's Space: - potential space which may first to involve during extension of Cholesteatoma, - bounded by, laterally, Shrapnell's membrane medially, Neck of Malleus superiorly, fibres of lateral malleolar fold inferiorly, lateral process of malleus
  14. 14. ANATOMY – External Ear ● Auricle / Pinna ● External Acoustic Canal ● Tympanic Membrane
  15. 15. ● Auricle (Pinna) - elastic fibrocartilage, two surfaces: medial & lateral surface - Lateral surface – characteristic prominences and depressions - Helix – most prominent outer part - Anti Helix – fold in front of helix - Concha – in front of anti-helix, hollow space divided by crus of helix - Cymba conchae & Cavum conchae - Tragus – cartilaginous projection anterior to Cavum concha - Scaphoid fossa – 'boat shaped' space b/w upper part of helix & anti helix - Incisura Terminalis – space b/w crus of helix and tragus
  16. 16. ● Cartilage – avascular, derives nutrients from perihondrium ● Trauma – 'Boxer's Ear' ● Two ligaments - Anterior Ligament - Posterior Ligament ● Muscles - Extrinsic Muscles - Auricularis Anterior - Auricularis Posterior - Auricularis Superior - Intrinsic Muscles
  17. 17. ● Blood Supply - Posterior Auricular Artery - Anterior Auricular branches of Superficial Temporal A - Superior Auricular Artery ● Nerve Supply - Greater Auricular N - Lesser Occipital N - Auriculotemporal N - Auricular branch of Vagus N (Arnold's N) - fibres from Facial N
  18. 18. ● External Auditory Canal: - from concha of auricle to TM - 2.4cm long, two parts – outer Cartilaginous and inner Bony part ● Cartilaginous Part: - outer 1/3 of EAC, 8mm - two deficiencies – 'Fissures of Santorim' ● Bony Part: - inner 2/3 of EAC, 16mm - Isthmus - Anterior Recess - Foramen of Huscke - Tympanic Sulcus
  19. 19. ● Tympanic Membrane: - medial end of EAC, partition b/w EAC and middle ear - obliquely set, forming an angle of 55 degree - 9-10mm tall, 8-9mm wide and 0.1mm thick Two parts: - Pars Tensa - Pars Flaccida ( Shrapnel's Membrane ) Three layers: - Outer Epithelial Layer - Middle Fibrous Layer - Inner Mucosal Layer
  20. 20. ● Pars Tensa: - Annulus Tympanicus - Umbo - four quadrants - 'cone of light' ● Pars Flaccida (Shrapnel's Membrane): - Anterior mallelolar fold - Posterior malleolar fold ● Nerve Supply: - Auriculotemporal N (Ant half of lat surface) - Auricular Br of Vagus N (Post half of lat surface) - Tympanic br of CN IX – Jacobson's N (med surface)
  21. 21. ANATOMY – Middle Ear ● ● ● Middle Ear Cleft – Middle ear(Tympanic cavity), Aditus, Antrum, Mastoid air cells Middle Ear/Tympanic cavity: irregular, air filled space within the temporal bone b/w TM laterally and osseous labyrinth medially. Contains auditory ossicles, intratympanic muscles
  22. 22. ● Middle Ear: 3 compartments - epitympanum (attic) : lies above level of malleolar fold - hypotympanum : lies below level of tympanic sulcus - mesotypmanum : lies opposite pars tensa
  23. 23. 6 surfaces – Roof, Floor, Medial, Lateral, Anterior, Posterior ● ● ● Roof – Tegmen tympani Floor – thin plate of bone seperating hypotympanum from dome of jugular bulb Anterior wall – thin plate of bone seperates from Internal Carotid A. Two openings – lower one for Eustachian tube, upper for canal of tensor tympani
  24. 24. ● Posterior wall – lie close to mastoid air cells, and has following structures: - Aditus - Fossa Incudis - Pyramid - Facial Recess ● Lateral wall - TM - Scutum
  25. 25. ● Medial wall – separates tympanic cavity from middle ear - Promontory - Oval window - Round window - Subiculum - Ponticulus - Canal for facial N - Processus cochleaformis - Sinus tympani
  26. 26. ● Mastoid Antrum: Air containing space in upper part of mastoid and communicates with attic through aditus - Roof: tegmen antri - Lateral wall: plate of bone on an avg 1.5cm thick in adults ● MacEwen's (suprameatal) triangle: bounded by - temporal line - posterosuperior segment of bony EAC - line drawn tangent to external canal
  27. 27. ● Aditus: - opening through which attic communicates with antrum. - Bony prominence of horizontal canal medially, - fossa incudis laterally - Facial N course below aditus
  28. 28. ● Contents of Tympanic Cavity: - Ossicles – Malleus, Incus, Stapes - Intratympanic muscles – Tensor tympani, Stapedius - Chorda tympani, - Tympanic plexus
  29. 29. ● Ossicles of middle ear - MALLEUS: head, neck, handle(manubrium), lateral and anterior process Head and neck of malleus lie in attic. Manubrium lies embedded in fibrous layer of TM Lateral process forms a projection and attaches to ant. & post. malleolar folds
  30. 30. - INCUS: - body, short process, long process - body and short process lies in attic - long process hangs vertically & attaches to head of stapes - STAPES: - head, neck, Ant. & Post. Crura, Footplate - footplate is held in oval window by annular ligament
  31. 31. ● INTRATYMPANIC MUSCLES: Tensor tympani - attaches to neck of malleus - tenses tympanic membrane - derived from 1st arch - supplied by branch of Mandibular N
  32. 32. Stapedius - attaches to neck of stapes - helps to dampen loud sound, preventing noise trauma to inner ear - derived from 2nd arch - supplied by branch of Facial N
  33. 33. ● Tympanic Plexus: - lies in the promontory - formed by: - tympanic br of gloosopharyngeal N - sympathetic fibres from plexus around ICA - supplies innervation to: - medial surface of TM, tympanic cavity, mastoid air cells & bony eustachian tube - carries secretomotor fibres for the parotid gland
  34. 34. ● Chorda tympani N: - Br of Facial N enters the middle ear through posterior canaliculus - runs on medial surface of TM b/w HOM and long process of incus - carries taste sensation from Ant. 2/3rd of tongue - secretomotor fibres to submaxillary and sublingual salivary glands
  35. 35. ● Blood Supply of Middle Ear: Anterior tympanic br of Maxillary A - supplies TM Stylomastoid br of Post Auricular A - supplies middle ear and mastoid air cells Minor vessels: ● ● ● ● Petrosal br of middle meningeal A Sup tympanic br of middle meningeal A Branch of Artery of pterygoid canal Tympanic br of ICA Veins: drain into pteryoid venous plexus & Superior petrosal veins
  36. 36. Thank You....

×