Inner ear

From greek.doctor
  • Fluid systems of the labyrinth
    • Membranous labyrinth
      • Filled with K-rich endolymph
      • Contains hair cells
      • Divided into vestibule and cochlear duct
    • Bony labyrinth
      • Contains membranous labyrinth in Na-rich perilymph
      • Three cavities
        • Scala media (cochlear duct)
          • Filled with endolymph
          • Basilar membrane forms the floor of it
        • Scala vestibuli
          • Filled with perilymph
          • Above and separated from scala media
          • Connected to scala tympani at helicotrema
        • Scala tympani
          • Filled with perilymph
          • Below and separated from scala media
          • Runs downward from helicotrema to the round window
    • Oval window vibrates -> sound waves transmitted in perilymph in scala vestibuli
      • -> sound waves vibrate the vestibular membrane and basilar membrane, thus stimulating hair cells
      • -> sound waves travel through helicotrema -> down the scala tympani -> to the round window
    • Low frequency waves act at apex of cochlea
    • High frequency waves act at base of cochlea
  • Toxic lesions of the inner ear
    • Etiology
      • Endogenous
        • Metabolic diseases
          • Diabetes mellitus
          • Uraemia
        • Bacterial toxins
      • Exogenous
        • Aminoglycosides
        • Loop diuretics
        • Cytostatic drugs
        • Salicylates
        • Industrial solvents
        • Heavy metals
        • Alcohol
        • Illegal drugs
    • Serous labyrinthitis
      • Bacterial toxins from chronic otitis media‎