INNER EAR - DR NITIN ANIYAN THOMAS (NATS)

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INNER EAR AND A DESCRIPTION ABOUT ANATOMY AND PHYSIOLOGY OF INNER EAR

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INNER EAR - DR NITIN ANIYAN THOMAS (NATS)

  1. 1. AR E ER Y HOM NN B T I N TI NI DR AS I nininni
  2. 2. INNER EAR  DEVELOPMENT OF INNER EAR Begins : 3rd week of fetal life Completes : 16th week Membraneous & Bony labyrinth develop from otic capsule Ectoderm in hind brain Auditory Placode Auditory vesicle differentiates - Endolymphatic duct & - sac
  3. 3. Semicircular ducts Utricle Saccule Cochlea Pars Superior Pars Inferior
  4. 4. INNER EAR / LABYBRINTH BONY & MEMBRANOUS LABYRINTH ENDOLYMPH BONY LABYRINTH VESTIBULE SEMI CIRCULAR CANALS COCHLEA seperated by PERILYMPH
  5. 5. Vestibular apparatus for balance and equilibrium Cochlea for hearing
  6. 6. A} VESTIBULE Central chamber Lateral wall : oval window Spherical- lodges saccule Medial wall : 2 Recessess Elliptical- lodges utricle Spherical R. – has perforated holes Maculae Cribrosa Media – inferior vestibular nerve Elliptical R. – Maculae Cribrosa Superior (Mike’s spot) – “Translabyrinthe” approach N to Utricle & ampulla
  7. 7. B} SEMI CIRCULAR CANALS Lie At to each other Rt Superior (15-20mm) Angles lateral (12-15mm) Posterior (18-20mm) lie lie transverse to petrous part of Temporal bone Parallel to petrous part of temporal bone bulge into aditus & antrum
  8. 8. Ampullated end-opens into vestibule Non Ampullated end of Supr & Post’r canals Unite – common channel – CRUS COMMUNE(4MM) C} COCHLEA Snail Lies Antr to bony labyrinth L=30mm Coiled tube 2.5 - 2.75 turns around central pyramid of bone MODILOUS – spirally –OSSEOUS SPIRAL LAMINA
  9. 9. base towards Int. Acoustic Meatus transmits cochlear vessels & nerves • Bony cochlea : 3 compartments Scala Vestibuli Scala Tympani Scala media (Membranous cochlea) - perilymph - communicate via cochlea apex HELICOTREMA Endolymph
  10. 10. MEMBRANOUS LABYRINTH Consists “ESCUSE” -Endolymphatic duct -Semi circular duct -Cochlear duct -Utricle -Saccule -Endolymphatic sac COCHLEAR DUCT / MEMBRANOUS COCHLEA / SCALA MEDIA • Coiled tube • Triangular on cross section • 3 walls :
  11. 11. Basilar memb – supports organ of corti - has sound receptors - thin inner part ZONA ARCUATA - thick outer part ZONA PECTINATA - seperates Scala tympani from scala media -its length from Basal coil (High freq sound) – Apical coil (low freq sound) Reissner’s membrane Seperates scala vestibuli - scala media Stria vascularis -Vascular epith. -Endolymph secretion Cochlear duct connects to saccule by DUCTUS REUNIENS
  12. 12. Organ of corti • Spead entirely over Basilar memb Has TUNNEL OF CORTI – consists of 2 rows of rods of inner & outer hair cells 1 row of inner hair cells & 3-4 rows of outer hair cells Inner rods-3500 Outer rods-12000 Hair cells supported by Pillar cells , Dieter cells , Hensens cells  Mechanical sound energy gets transduced into electrochemical energy
  13. 13. TECTORIAL MEMBRANE • Has gelatinous matrix with fibers • Lies above Organ of corti • Its undersurface attaches to tip of outer hair cells Shearing force b/w them stimulates hair cells
  14. 14. UTRICLE & SACCULE Both lie in bony vestibule but saccule lies anterior to utricle Utricule connects to saccule via UTRICOSACCULAR DUCT Cochlear duct connects to saccule via DUCTUS REUNIENS Utricle has 5 openings of 3 semicircular canals Spherical recess-Saccule (S-S) Elleptical recess-Utricle U – lies horizontally Its vestibular receptor organ MACULA S- lies vertically Linear acceleration & decelaration Has hair cells + supporting cells + gelatinous mass secreted by has Mucopolysaccharides
  15. 15. Gelatinous mass – also contains – CaCO3 crystals OTOLITH / STATACONIA
  16. 16. ENDOLYMPHATIC DUCT & SAC • Union of 2 ducts (1 from saccule and 1 from utricle) • Pass through Vestibular Aqueduct • Terminal end – dilated – forms ENDOLYMPHATIC SAC
  17. 17. SEMICIRCULAR DUCTS 3 in number Open in utricle Ampullated end – has thick neuroepithelium – CRISTA AMPULLARIS Hair cells + Supporting cells + Gelatinous mass dome shaped In cristae CUPULA
  18. 18. HAIR CELLS 2 types type 1 (FLASK SHAPED) Summit Hair cells type 2 (CYLINDRICAL) CRISTAE 1 KINOCILIUM Periphery Many STEREOCILIA (60-110)
  19. 19. Inner hair cells – Afferent Cochlear fibers – transmit auditory impulses Outer hair cells – Efferent fibers – modulate inner hair cells fx Supporting cells Dieters cell - lie in b/w outer hair cells Outside it - Hensens cells lie
  20. 20. MECHANISM OF HEARING TM SOUND PINNA AUDITORY N. EAC Vibration of TRANSDUCTION Pr. Changes in OSSICULAR CHAIN FOOT PLATE OF STAPES LABYRINTHINE FLUID STIMULATES HAIR CELLS OF BASILAR MEMB.MOVES ORGAN OF CORTI COCHLEAR NUCLEI - SUPR. OLIVARY COMPLEX – LAT. LEMNISCUS – INFR. COLLICULUS AUDITORY CORTEX (AREA 41 / BROADMANN’S AREA) MEDIAL GENICULATE BODY
  21. 21. BLOOD SUPPLY LABYRINTHINE @ {Br. Of Antr Infr Cerebellar @} common cochlear Antr Vestibular @ {Utricle , Supr & Lateral Canal} Vestibulo cochlear Cochlear br. { 20% Cochlea} Main cochlear { 80% Cochlea} Postr Vestibular @ {Saccule ; Postr Canal}

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