Anatomy of Inner Ear

 Anatomy :  2 parts :             i ) Membranous 

                                               ii) Bony 

    Membranous labyrinth is the actual inner ear . Bony labyrinth is the bony cover of membranous labyrinth .  



  Fluids of inner ear : Inner ear filled with endolymph and surrounded by perilymph .

 Stria vascularis of Cochlea secretes Endolymph which is present in endolymphatic space .Perilymph = CSF 

 NOTE :Perilymph is connected to CSF through

aqueduct of cochlea . That is why in a case of 

 meningitis deafness can occur . So BERA 

 should be done before discharge .



Endolymph has high Potassium low sodium . 

 Perilymph has high Sodium and low potassium.

(Tips : How to remember it?  Everyone of us 

 knows that interior of a cell contain higher Potassium So Endolymph also . " Interior = Endo" --> just to remember ;-) .) 

  # Basal turns senses higher frequencies 

 # Appex -Low frequency 

 Physiology of hearing is explained by Travelling Wave Theory given by VON BEKESY


Note : Helicotrema is the apex of cochlea .

  Utricle and Saccule :     Function of Saccule = vertical movement 

                                           Function of Utricle =  Horizontal movement 

 Microscopic structure of macula (=sensory end organ ) : 



If Calcium Carbonate crystals ( Otoconia or Otolith ) turn free and reach semicircular canal it will lead to vertigo . This disease is called Benign Paroxysmal Positional Vertigo .

   Benign Paroxysmal Positional Vertigo :  # Posterior semicircular canal most commonly involved . 

 # Dix Hallpike maneuver  is diagnostic . # Epley maneuver or Semont maneuver is for treatment (= particle positioning maneuver )




Semicircular canals  :

   3 in numbers : i0 lateral ii) posterior iii) superior 

 Solid angle = angle between 3 canals . 

 Microscopic structure of Crista :  


Fitzgerald bithermal caloric test : For lateral semicircular canal only




  Tips  : Normal  Direction of nystagmus 

                                    COWS  Cold - opposite 

                                                   Warm - Same side 

 Note : Electrical recording of Nystagmus is called Electronystagmogram and plotted in Butterfly chart .  




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