2015 Hearing & Balance

Organ of Corti

Organ of Corti Schematic

The key mechanical elements involved in signal transduction in the cochlea are:

  • BASILAR MEMBRANE (BM): resonates when sound is being transduced
  • TECTORIAL MEMBRANE (TM): gelatinous material that extends from the spiral limbus (SL) over the apical surface of the hair cells
    • the stereocilia of the outer hair cells (OHC) are embedded in the TM, which allows a solid, physical connection between the tectorial and basilar membranes
    • the stereocilia of the inner hair cells (IHC) are close enough to the TM that they brush against it when the BM vibrates
    • MN = marginal net of the tectorial membrane
  • PILLAR CELLS (IP1, OP1): form the tunnel of Corti (also called the inner tunnel) and provide structural support for the reticular lamina that extends across the apical surface of hair cells, pillar and Hensen cells and the Deiter cell processes
  • DEITER CELLS: outer hair cells sit in the sockets of the Deiter cells, but are otherwise free from the supporting cells (unlike the inner hair cells that are embedded in the supporting cells of the inner sulcus
  • HENSEN CELLS: form the outer rim of the reicular lamina

The reticular lamina forms the boundary between endolymph (salmon colour) and perilymph (blue). Tight junctions prevent mixing of the two fluids. The stereocilia are in endolymph, but the hair cell bodies are in perilymph. Potassium ions flowing through the hair cells during transduction are recycled back to the scala media via the supporting cells and the stria vascularis.

SEM Cochlear Hair Cells
  • view of the apical surface of the hair cells and pillar cells (tectorial membrane has been peeled away) to show the stereocilia
  • 1 row of inner hair cells throughout the entire length of the cochlea
    • inner hair cell stereocilia form a straight line (right side)
  • 3-5 rows of outer hair cells; more rows in the apex, where the basilar membrane is wider
    • outer hair cell stereocilia form a "W" pattern, with the wide part of the "W" facing the tunnel of Corti
Email: Dr. Janet Fitzakerley | ©2015 University of Minnesota Medical School Duluth | Last modified: 24-jan-15 5:16 PM