Anatomy of inner ear


Published on

Published in: Health & Medicine, Business
1 Comment
  • My dear, How are you today? i will like to be your friend My name is Sheikha Ghunaim , am a 43 years old divorcee. Please write to me in my email ( ). im honest and open mind single woman. im going to tell more when i see your response. Regards Sheikha.
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide
  • The inner ear consists of a membranous “labyrinth” encased in an osseous labyrinth.
  • The vestibule and semicircular canals are concerned with vestibular function (balance); the cochlea is concerned with hearing. The cochlea is a coiled tube. Notice that the oval window and round window open into the vestibule, at the base of the cochlea.
  • Maculae cribrosa media for inferor vestibular nerve Elliptical recess posteriorly ,lodges utricle Macula cribrosa superior (mike’s dot )-passage of ns of utricle and ampulla of superior and lateral SCC Vestibular crest and cochlear recess Aquaduct of vestibule below elliptical recess Anterior and posterosuperior
  • It is 12-15 mm long. Projects as rounded bulge in middle ear,aditus & antrum. Makes an angle of 30 with horizontal plane. Anterior end is ampulated and opened in upper part of vestibule. Posterior end is non ampullated & ends in lower part of vestibule below the orifice of crus cummune.
  • It is 18-22 mm long. Situated parallel and close to the posterior surface of petrous temporal bone lower end is ampulated and opened into lower part of vestibule Upper limp joins the crus cummune along with superior scc
  • Reissner’s membrane and the basilar membrane divide the the cochlea longitudinally into three scalae. Movement of the the basilar membrane by pressure changes induced by stapes footplate motion at the oval window is a critical step in the transduction process
  • Notice that scala media is more or less triangular, formed by Reissner’s membrane, basilar membrane and the structure called the stria vascularis. The fluid that fills scala tympani and scala vestibuli is called perilymph; the fluid that fills scala media is called endolymph. The organ of Corti rests on the basilar membrane within scala media.
  • the length increases as it proceeds from the basal coil to apical coil , so higher frequency of sound are heard at the basal coil while lower tunes at the apical coil. Inner thin area is called zona arcuate while outer thick area called zona pectinata.
  • If you cut the cochlear tube cross sectionally, you’d see something like this. Scala vestibuli on top, scala tympani on the bottom. Scala media is a triangular duct in the middle. The process of transduction occurs in the structures within scala media, sitting on the basilar membrane -- these structures comprise the organ of Corti. The side of the duct where the nerve fibers exit (left in this picture) is the “inner” or “modiolar” side of the duct. The opposite side is the “outer” side.
  • Oblong and irregular Has anteriorly upward slope at an apparent angle of 30 It lies in posterior part of bony vestibule & recieves the five openings of three SCC Utricle(4.33 mm) is bigger than saccule (2.4 mm) & lies superior to saccule Utricle connected to saccule via utriculosaccular duct Its sensory organ macula is concerned with linear acceleration & decelaration.
  • Two types of cells in the organ of Corti are support cells and hair cells. The hair cells are the “receptor” cells-- the ones that transduce sound. Support cells such as the Deiter’s cells support hair cells. The tops of the hair cells and pillar cells form the reticular lamina, which isolates the hair cells’ stereocilia from their cell bodies. The tectorial membrane is loosely coupled to the reticular lamina. Endolymph & perilymph. There are 4 rows of hair cells, one on the inner (modiolar) side of the tunnel formed by the pillar cells-- these are the inner hair cells; and 3 one the outer side of the Tunnel of Corti, these are the outer hair cells. Notice that the Deiter’s cells support the Outer hair cells at their base, but that the outer hair cell walls are surrounded by fluid. The inner hair cell is surrounded by support cells.
  • The reticular lamina is a solid surface at the tops of the hair cells, so the tops of the hair cells are in endolymph and the bottom of the hair cells are in perilymph.
  • Deiter’s cell processes “fill in the gaps” between the tops of the outer hair cells to form the reticular lamina.
  • Outer hair cells, supported by Deiter’s cells, form “columns” between the basilar membrane and the reticular lamina.
  • Stereocilia on inner (left) and outer (right) hair cells. Stereocilia are arranged in curved or v-shaped rows that face toward the modiolus.
  • Each row of stereocilia is taller than the next. The tip of each stereocilium is linked to the side of the stereocilium behind it by a tip link.
  • Nerve fibers exit the organ of Corti on the modiolar side.
  • In the auditory nerve, the dendrites contact the hair cells. The cell bodies form what is called the spiral ganglion, and the axons form the auditory nerve that connects the ear to the brainstem. The “contact” points between the dendrites and the hair cells or between the axons of one neuron and the dendrites of another are called synapses. Synapses have specialized structures and substances that allow communication between receptors and neurons or between neurons.
  • The cell bodies of the neurons that form the auditory nerve are located within the cochlear modiolus. The collection of cell bodies is called the spiral ganglion.
  • Different types of nerve fibers innervate IHCs and OHCs. Type I fibers innervate IHCs; Type II neurons innervate OHCs.
  • Nearly all of the nerve fibers that carry messages from the ear to the brain innervate inner hair cells. Notice that the many nerve fibers that contact one inner hair cells do not branch to other inner hair cells. Each IHC has its own “private” set of fibers. The Type II nerve fibers innervate many OHCs. and the OHCs they innervate are basal to the point at which the nerve fiber enters the cochlea.
  • Thin fibers attach toward modiolar side, thick fibers toward outer side of IHC.
  • Neurons from the brainstem also contact hair cells. These neurons carry information from the brain to the ear and are called efferent neurons. The vast majority of efferents innervate OHCs, and the contacts on OHCs differ from those on IHCs. Efferents form large calyx-shaped contacts on the OHC cell body; efferents form small bouton-like contacts on the afferent nerve fibers that contact IHCs.
  • The nuclei shown here are in a part of the brainstem called the superior olivary complex. Fibers from both sides of the brain innervate both IHCs and OHCs, but the fibers innervating the two types of HC originate in different places. One recent study suggests that the SOC receives input from auditory cortex-- so fairly high level processing. The fiber tract containing the efferent fibers is known as the olivocochlear bundle (OCB). The tract from the same side of the brain is called the uncrossed OCB and the tract from the opposite side of the brain is called the crossed OCB.
  • .
  • .
  • Anatomy of inner ear

    1. 1. The Inner EarThe Inner Ear
    2. 2. The Inner Ear(Labrynth)
    3. 3. The Inner Ear(Labrynth) Bony labrynth Membraneous labrynth
    4. 4. Bony labyrinth: Hard, bony outer shell. Membranous labyrinth: Fully contained inside the bony labyrinth; like a convoluted-shaped water balloon stuff inside the bony labyrinth. (from Minifie, Hixon, & Williams, 1973)
    5. 5. Parts of the Bony labrynth
    6. 6. labrynth • Lateral wall of labrynth is formed by medial wall of middle ear • Medial wall is formed by lateral limit of internal auditory canal (IAC)
    7. 7. Vestibule • Central chamber of labrynth (5 mm) • Lateral wall contains oval window(fenestra vestibuli) – closed by footplate of stapes sorrounded by annular ligament.
    8. 8. Vestibule-medial wall
    9. 9. Semicircular canals • Lateral(horizontal) • Posterior • Superior(anterior).
    10. 10. Semicircular canals • Occupies 2/3 rd of a circle. • 0.8 mm in diameter. • Lie in planes at right angles. • Has ampullated (contain cristae) and non ampullated ends. • All three ampullated ends and non ampullated ends of lateral SCC open independently and directly into vestibule. • Involved in angular acceleration and balance
    11. 11. Superior SCC  It is 15-20 mm long  Situated transverse to the axis of petrous part of temporal bone.
    12. 12. Lateral SCC
    13. 13. posterior SCC
    14. 14. Crus cummune ?  the non ampullated ends of posterior and superior canals join & form this (4 mm length)  Opens into medial part of vestibule.  So three SCC opens into vestibule by 5 openings.
    15. 15. The Cochlea • Snail shaped coiled tube • 2.5 to 2.75 turns round a central pyramid of bone called modiolus. • 30 mm long • 5 mm from base to apex & 9 mm around its base
    16. 16. Modiolus ?  Central pyramid of bone around which cochlea forms  The base of modiolus directed towards internal acoustic meatus  Transmits vessels and nerves to cochlea  Apex lies medial to tensor tympani
    17. 17. Osseous spiral lamina ?  A thin plate of bone winds spirally around modiolus like the thread of a screw .  This bony lamina gives attachment to the basilar membrane and divides the bony cochlea tube into three compartments. 1. Scala vestibuli 2. Scala tympani 3. Scala media (membraneous cochlea)
    18. 18.
    19. 19. Rosenthal’s canal ?  Spiral ganglions are situated in this canal which runs along the osseous spiral lamina.
    20. 20. The cochlea uncoiled
    21. 21. Scala vestibuli ?  This uppermost channel is continuous with vestibule and closed at oval window by stapes footplate
    22. 22. Scala tympani ?  This lowermost channel is closed by secondary TM of round window
    23. 23. Scala media ?  Bind coiled tube, connected to the saccule via ductus reunions.
    24. 24. aqueduct of cochlea?  A bony bulge in the medial wall of middle ear , represents the basal coil of cochlea. promontory ?  Scala tympani is connected with subarachnoid space via this.  It is thought to regulate perilymph & pressure in bony labrynth.
    25. 25. Membraneous labrynth
    26. 26. Membranous labyrinth with the entire bony labyrinth stripped away.
    27. 27. Parts of the Membraneous labrynth Cochlear duct Utricle Saccule Three semicircular canals Endolymphatic duct and sac
    28. 28. Cochlear duct
    29. 29. Cochlear duct-relations & boundaries 1. Basilar membrane – base  It supports organ of corti 2. Reissners membrane  Seperates scala media from scala vestibuli 3. Stria vascularis  It contains vascular epithelium and secretes endolymph
    30. 30.
    31. 31. Notice the stria vascularis (also area vascularis) – The s.v. secretes endolymph. Notice also the spiral ligament, which attaches the b.m. to the bony wall of the cochlea, and the limbus (or limbus spiralis), a fibrous covering of the spiral lamina. modiolus spiral ligament
    32. 32. Cross-section of the cochlear duct
    33. 33. utricle  Oblong and irregular  Has anteriorly upward slope at an apparent angle of 30  It lies in posterior part of bony vestibule & recieves the five openings of three SCC  Utricle(4.33 mm) is bigger than saccule (2.4 mm) & lies superior to saccule  Utricle connected to saccule via utriculosaccular duct  Its sensory organ macula is concerned with linear acceleration & decelaration.
    34. 34. saccule  lies anterior to utricle opposite the stapes footplate in the bony vestibule.  its sensory organ macula is concerned with linear acceleration & decelaration.  Saccule is connected to the cochlea via a thin reunion duct.
    35. 35. Semicircular ducts  Three SC ducts , which open in the utricle correspond exactly to the three bony canals  The ampullated end contains a thickened ridge of neuroepithelium which is called crista ampullaris.  Crista ampullaris is concerned with angular acceleration & decelaration.
    36. 36. Endolymphatic duct and sac  Ducts from utricle and saccule unites and form utriculosaccular duct Continues as endolymphatic duct that passes via the vestibular aqueduct
    37. 37. The terminal part of the endolymphatic duct is dilated and forms endolymphatic sac , which is situated between two layers of dura on the posterior surface of petrous bone.
    38. 38. Inner ear fluids  perilymph – between bony and membraneous labrynth  Endolymph fills the entire membraneous labrynth perilymph endolymph Resembles ECF Resembles ICF Rich in sodium ions Rich in pottasium ions
    39. 39.
    40. 40. Organ Of Corti • The end organ of hearing – Contains stereocilia & receptor hair cells – 3 rows OHC, 1 row IHC – Tectorial and Basilar Membranes – Cochlear fluids
    41. 41. A closer look at the organ of Corti
    42. 42. Detail of the Organ of Corti (from Stevens,1951) Any cut through the cochlea will show 1 inner hair cell (IHC) and 3 (sometimes 4) outer hair cells (OHCs). This unit – 1 IHC and 3-4 OHCs is referred to as a hair cell channel. There are about 3000 channels in the human cochlea. (That number will become important later when we discuss cochlear implants.)
    43. 43.
    44. 44. Reticular lamina
    45. 45. Deiter’s cells
    46. 46. Arrangement of hair cells
    47. 47. Stereocilia
    48. 48. Arrangement of stereocilia
    49. 49.
    50. 50. Another view...
    51. 51. Cochlea • The cochlea contains an array of highly specialized cells arranged in a highly specialized manner. • There are structural differences between IHCs and OHCs that suggest that they differ in function • The cochlea not only sends a message to the brain, but it may also receive messages from the brain via efferent innervation.
    52. 52. Innervation of the organ of Corti Nerve fibers
    53. 53. Neuron review From Gelfand (1998)
    54. 54.
    55. 55. The spiral ganglion
    56. 56. Pattern of afferent innervation
    57. 57. Pattern of afferent innervation
    58. 58. There are differences among the fibers innervating an inner hair cell
    59. 59. Pattern of efferent innervation
    60. 60. Sources of efferent cochlear innervation
    61. 61. Vestibular receptors
    62. 62. Blood supply of labrynth
    63. 63. Blood supply of labrynth  Mainly by internal auditory artery (branch of AICA <branch of basilar artery>)  Internal auditory artery divides into 1. Anterior vestibular artery  Supplies utricle ,superior & lateral SCC 2. Common cochlear artery  Main cochlear artery(80%)-supplies cochlea  Vestibulocochlear artery 1. Post vestibular artery-supplies saccule & post SCC 2. Cochlear branch –supplies to
    64. 64. Venous drainage  Internal auditory vein  Vein of cochlear aquaduct  Vein of vestibular aquaduct Drain into inferior petrosal and sigmoid sinuses
    65. 65. Internal auditory canal  About 1 cm long  Passes into petrous part of temporal bone in a lateral direction  Lined by dura
    66. 66. Internal auditory canal  At its lateral end (fundus) IAC is closed by a vertical cribriform plate of bone that seperates it from labrynth  A transverse crest divides this plate into smaller upper and larger lower part  Upper part is again divided into ant & post part by a vertical crest called BILL’S BAR.
    67. 67. IAC - Contents  Vestibulocochlear Nerve  Facial nerve including nervus intermedius  Internal auditory artery and vein
    68. 68. Development of inner ear  Initially membraneous labrynth , followed by encasement by bony labrynth.  Starts within first few days( 22- 23 days) Ectodermal thickening in hind brain Otic placode Otic pit Oticyst Membraneous labrynth (by 25 th week of GA)
    69. 69. Development of inner ear
    70. 70. Development of inner ear  BONY LABRYNTH  Mesenchyme enclosing the otocyst becomes chondrified to form otic capsule Ossification begins in around 16 th week  Certain channels remain within otic capsule like oval window where part of the otic capsule becomes the stapes footplate and the annular ligament.
    71. 71. THANK YOU
    72. 72.
    73. 73.
    74. 74. Inner Ear Disorders: Prenatal Causes • Genetic mutation/inheritance • Cytomegalovirus (CMV) • Rubella • Rh incompatibility
    75. 75. Anatomical Anomalies Often seen as Bony malformations Examples: Mondini (incomplete cochlea) Enlarged Duct (shown here)
    76. 76. Mondini Aplasia • AD • Most common cochlear abnormality • Progressive or fluctuating HL •  risk of perilymphatic gusher and meningitis from dilated cochlear aqueduct • Dx: CT reveals single turned cochlea, no interscalar septum • Tx: HA, cochlear implant
    77. 77. Age Effects
    78. 78. Noise Damage • Temporary Threshold Shift (TTS) • Permanent Threshold Shift (PTS) • Duration, Timing and Intensity influence • Typical “Noise Notch” often seen between ____________ first. • Notch widens and deepens over time, with hearing loss spreading to adjacent frequencies, and increasing in degree.
    79. 79. Inner Ear Disorders • Noise induced • Miniers disease • ototoxicity