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Cross-section of Cochlea

Ductus Cochlearis (membranous cochlea; scala media)

  • ductus cochlearis consists of a spirally arranged tube enclosed in the bony canal of the cochlea and lying along its outer wall.
  • osseous spiral lamina extends only part of the distance between the modiolus and the outer wall of the cochlea
  • basilar membrane stretches from its free edge to the outer wall of the cochlea, and completes the roof of the scala tympani.
  • vestibular membrane (Reissneri), a second and more delicate membrane, extends from the thickened periosteum covering the osseous spiral lamina to the outer wall of the cochlea
    • it is attached at some little distance above the outer edge of the basilar membrane.
  • ductus cochlearis or scala media (Fig. 928) is the canal thus shut off between the scala tympani below and the scala vestibule above
    • triangular on transverse section, its roof being formed by the vestibular membrane
    • outer wall by the periosteum lining the bony canal
    • floor by the membrana basilaris and the outer part of the lamina spiralis ossea.
    • extremities are closed; the upper is termed the lagena and is attached to the cupula at the upper part of the helicotrema; the lower is lodged in the recessus cochlearis of the vestibule.
  • canalis reuniens of Hensen (Fig. 924) a narrow, short canal, located at the lower end the ductus cochlearis brought into continuity with the saccule.
  • On the membrana basilaris is situated the spiral organ of Corti.
  • The vestibular membrane is thin and homogeneous, and is covered on its upper and under surfaces by a layer of epithelium.
  • The periosteum, forming the outer wall of the ductus cochlearis, is greatly thickened and altered in character, and is called the spiral ligament.
    • projects inward below as a triangular prominence, the basilar crest, which gives attachment to the outer edge of the basilar membrane
    • immediately above the crest is a concavity, the sulcus spiralis externus.
    • stria vascularis forms the upper portion of the spiral ligament contains numerous capillary loops and small bloodvessels.



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Reference

Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.


Cite this page: Hill, M.A. (2019, June 16) Embryology Gray0928.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Gray0928.jpg

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