2015 Hearing & Balance

Scala media

Critical fact icon There are 3 critical functional regions in and around the scala media. The organ of Corti contains the sensory hair cells that transduce sound into a receptor potential. The spiral ganglion contains the cell bodies of the sensory neurons that send action potentials to the brainstem. The stria vascularis produces endolymph and generates the endocochlear potential.
Cross section one cochlear turn
Organ of Corti histology
  1. organ of Corti:
    • sits on top of the basilar membrane across its entire width: extends from the spiral limbus (inner sulcus region) to the spiral ligament of the lateral wall (outer sulcus region)
    • moves when the basilar membrane vibrates
    • given rigidity by an arch that separates the inner (type I) hair cells from the outer (type II) hair cells
    • has numerous, varied supporting cells in addition to the hair cells

  2. spiral ganglion:
    • found medial to the spiral limbus, inside the modiolus
    • peripheral processes of the spiral ganglion neurons extend from the hair cells into the ganglion
      • fibres are myelinated until they pass through the habenula perforata to reach the hair cells
    • central processes form the auditory branch of the VIII cranial nerve

  3. stria vascularis:
    • forms the medial boundary of the lateral wall, adjacent to the spiral ligament
    • critical part of the potassium recycling system that moves K+ into the scala media in order to maintain the high K+ concentrations of the endolymph
    • generates the endocochlear potential
Email: Dr. Janet Fitzakerley | ©2015 University of Minnesota Medical School Duluth | Last modified: 24-jan-15 5:16 PM