1. ANATOMY OF INNER EAR Dr. Supreet Singh Nayyar, AFMC for more presentations, visit www.nayyarENT.comwww.nayyarENT.com 20-07-2012www.nayyarENT.com

2. Organ concerned with hearing and balance Consists of : a) Bony Labyrinth b) Membranous Labyrinth 20-07-2012www.nayyarENT.com

3. BONY LABYRINTH Consists of : a)Vestibule b)Semicircular Canals c)Cochlea 20-07-2012www.nayyarENT.com

4. SALIENT FEATURES 20-07-2012www.nayyarENT.com

5. MEMBRANOUS LABYRINTH Consists of : a) Cochlear Duct b) Utricle & Saccule c) Semicircular Ducts d) Endolymphatic duct & Sac 20-07-2012www.nayyarENT.com

6. STRUCTURE OF THE COCHLEAR DUCT Subdivided into: Scala tympani, Scala vestibuli & Scala media Scala media is triangular in cross section 20-07-2012www.nayyarENT.com

7. REISSNER’S MEMBRANE Separates Scala media from Scala tympani Runs obliquely Extends from spiral limbus to lateral wall Consists of 2 layers of cells separated by basement membrane 20-07-2012www.nayyarENT.com

8. BASILAR MEMBRANE Acellular layer Stretches from osseous spiral lamina to the spiral prominence Organ of Corti is situated on the upper surface Stretches from spiral limbus to Claudius cells Below it lie spindle shaped cells (tympanic cells) & a branching spiral vessel 20-07-2012www.nayyarENT.com

9. SPIRAL LIMBUS Composed of interdental cells & main body of connective tissue cells & blood vessels embedded in an ECM Concave side forms the Inner Sulcus Convex surface forms Tectorial membrane 20-07-2012www.nayyarENT.com

10. STRIA VASCULARIS Forms the lateral boundary Composed of 3 layers of cells: Marginal cells Intermediate cells Basal cells Spiral ligament (fibrocytes & connective tissue) on the outer side Contains a variety of ion pumps, enzymes & transport proteins 20-07-2012www.nayyarENT.com

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12. CELLULAR ARCHITECHTURE AND FUNCTION OF ORGAN OF CORTI Sensory region consists of 2 types of sensory hair cells with apical stereocilia Stereocilia project into the overlying endolymph Inner hair cells form a single row while outer hair cells form 3-4 rows Separated by 2 rows of pillar cells from the Tunnel of Corti 20-07-2012www.nayyarENT.com

13. SUPPORTING CELLS Associated with hair cells Inner phalangeal cells & border cells enclose inner hair cells Deiters’ cells enclose outer hair cells & send phalangeal processes to the adjacent cells Hensen’s cells & Claudius’ cells are present on the outer edge of basilar membrane 20-07-2012www.nayyarENT.com

14. OUTER HAIR CELLS Cylindrical cells with flattened upper surface Sensory upper end & synaptic pole at basal end Stereocilia arranged in V or W shaped rows In contact with the undersurface of tectorial membrane 20-07-2012www.nayyarENT.com

15. STEREOCILIA Cylindrical Bevelled tip with narrow ankle region Angled towards each other Connected by tip links & lateral links Membrane contains proteins associated with calcium control & mechanosensitivity 20-07-2012www.nayyarENT.com

16. INNER HAIR CELLS Flask shaped Flattened or concave apical surface 3-4 linear rows of stereocilia Cell bodies are rich in ER, golgi bodies, mitochondria, Synaptic pole at the basal end 20-07-2012www.nayyarENT.com

17. ULTRASRUCTURE OF SUPPORTING CELLS Phalangeal processes: microtubular bundles Deiters’ cell cup: Actin- rich core Inner phalangeal & border cell membranes: associated with IHC membranes Finger-like projections: interdigitate with afferent nerve auditory nerve fibres Pillar cells: Thick microtubular bundles with radial feet & arching above 20-07-2012www.nayyarENT.com

18. INNERVATION OF ORGAN OF CORTI Acoustic information from hair cells is transferred by the auditory portion of the VIIIth nerve to the ipsilateral cochlear nuclear complex in the brain stem Composed of afferent fibres from spiral ganglion neurones Types of Neurones: Type I and II 20-07-2012www.nayyarENT.com

19. ANATOMY AND ULTRASTRUCTURE OF THE VESTIBULAR ORGAN Delicate system of membranous ducts containing sensory epithelia or machanoreceptors Important for the sense of gravity and balance Sensory epithelium located in the 3 ampullae, semicircular canals and in the maculae of saccule and utricle 20-07-2012www.nayyarENT.com

20. FUNCTIONS OF HUMAN VESTIBULAR ORGAN Human Vestibular Labyrinth Function Receptor for Gravitation & other Linear Accelerations Receptor for Angular Accelerations Regulates Tonus of Body Musculature 20-07-2012www.nayyarENT.com

21. UTRICLE Oblong & irregular; superior to the saccule Slopes anteriorly upwards at an angle of 30 degrees Macula utriculi lies in a horizontal plane Mean area: 4.30 mm² Contains approx. 33,000 hair cells 20-07-2012www.nayyarENT.com

22. SACCULE Hook shaped Lies virtually in a vertical position Mean area of saccular macule: 2.4 mm² Contains approx.18,000 hair cells Overlying the neuroepithelium is a calcareous material consisting ‘otoconia’ Partially anchored in a gelatinous substance forming otoconial membrane Hair processes of sensory cells project into it 20-07-2012www.nayyarENT.com

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24. OTOCONIAL LAYER Gelatinous layer, a subgelatinous space and otoconia Consists of an organic protein matrix along with inorganic calcium carbonate crystallized in the form of ‘calcite’ Secreted from apical cytoplasm of adjacent supporting cells with CA Degenerative changes with aging & disease Otoconial turnover occurs with the help of ‘dark cells’ 20-07-2012www.nayyarENT.com

25. SRUCTURE AND FUNCTION OF THE AMPULLA AND CUPULA Superior opening of horizontal & superior semicircular canal, and inferior opening of posterior canal widen to form Ampulla 20-07-2012www.nayyarENT.com

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27. VESTIBULAR SENSORY CELLS TYPE I CELLS: Flask shaped Surrounded by nerve chalice Collateral extensions on Type II cells TYPE II CELLS: Synapse with the collaterals & with the membranes of the chalices Cylindrical 20-07-2012www.nayyarENT.com

28. VESTIBULAR NERVE Contains approx. 18,000 afferent fibres Vestibular ganglion or Scarpa’s ganglion consist of bipolar neurons Consists superior & inferior groups of cells associated with superior & inferior vestibular nerve. Nerves contain both large & small fibres Vestibular & cochlear nerves merge in the IAM Human vestibular nerve contains efferent fibres supplying both the cochlear & vestibular sensory organs 20-07-2012www.nayyarENT.com

29. VASCULAR SUPPLY OF LABYRINTH 20-07-2012www.nayyarENT.com

30. THANK YOU For more presentations, visit www.nayyarENT.com www.nayyarENT.com 20-07-2012www.nayyarENT.com