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Inner Ear
  • Consists of the acoustic apparatus , the cochlea housing the cochlear duct for auditory sense, and the vestibular apparatus , the vestibule housing the utricle and saccule, and the semicircular canals housing the semicircular ducts for the sense of equilibrium.
  • Is the place where vibrations are transduced to specific nerve impulses that are transmitted through the acoustic nerve to the central nervous system (CNS).
  • Is composed of the bony labyrinth and the membranous labyrinth.

A. Bony labyrinth
  • Consists of three parts: the vestibule, the three semicircular canals, and the cochlea, all of which contain the perilymph , in which the membranous labyrinth is suspended.
  • The vestibule is a cavity of the bony labyrinth communicating with the cochlea anteriorly and the semicircular canals posteriorly.
  • The bony cochlea consists of two adjacent ducts: (a) the upper scala vestibuli , which begins in the vestibule and receives the vibrations transmitted to the perilymph at the oval window; and (b) the lower scala tympani , which communicates with the scala vestibuli through the helicotrema at the apex of the cochlea and ends at the round window, where the sound pressure waves are dissipated.
B. Membranous labyrinth
  • Is suspended in perilymph within the bony labyrinth, is filled with endolymph , and contains the sensory organs.
  • Has comparable parts and arrangement as the bony labyrinth.
  • Its utricle and saccule are dilated membranous sacs in the vestibule and contain sense organs called maculae , which detect linear acceleration of the head. The macula of the utricle has a horizontal orientation, and the macula of the saccule has a vertical orientation.
  • Its semicircular ducts consist of anterior (superior), lateral, and posterior ducts, and their dilated ends are called ampullae , which detect rotational or angular acceleration.
  • Its cochlear duct (scala media) is wedged between the scala vestibuli and scala tympani and contains endolymph and the spiral organ of Corti , with receptor cells (hair cells) for auditory stimuli (the sense of hearing).

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AndyC
AndyC 		Latest page update: made by AndyC , Apr 25 2011, 1:14 AM EDT (about this update About This Update AndyC Edited by AndyC

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