• 15 parts
  • Checked September 2026

Cochlea Diagram

The cochlea uncoiled, cut through its turns, and enlarged down to the hair cells.

Cochlea Diagram

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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Write the name of each numbered part.Answer key

  1. Scala vestibuli
  2. Cochlear duct (scala media)
  3. Scala tympani
  4. Helicotrema
  5. Oval window
  6. Round window
  7. Modiolus
  8. Spiral ganglion
  9. Cochlear nerve
  10. Vestibular membrane (Reissner's membrane)
  11. Organ of Corti (spiral organ)
  12. Basilar membrane
  13. Tectorial membrane
  14. Inner hair cells
  15. Outer hair cells

Drawn for this site on 2026-09-30 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

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Chambers and windows 6

  1. Scala vestibuli It runs above the cochlear duct to the tip of the cochlea.
  2. Cochlear duct (scala media) It holds the organ of Corti. Its fluid is endolymph.
  3. Scala tympani It runs under the cochlear duct. It goes from the tip of the cochlea back to its base.
  4. Helicotrema Here the scala vestibuli becomes the scala tympani. It curves over the end of the cochlear duct.
  5. Oval window Its movement sets up waves in the scala vestibuli.
  6. Round window It bulges out and in as the fluid moves.

The core and its nerve 3

  1. Modiolus The cochlea makes two and three-quarter turns round it.
  2. Spiral ganglion Its cells send fibers out to the organ of Corti. They also send fibers in to the cochlear nerve.
  3. Cochlear nerve It carries hearing signals toward the brain.

Membranes and hair cells 6

  1. Vestibular membrane (Reissner's membrane) It separates the cochlear duct from the scala vestibuli.
  2. Organ of Corti (spiral organ) Its hair cells turn the movement of the membrane into nerve signals.
  3. Basilar membrane Sound makes it move. High notes near the base of the cochlea, low notes near the tip.
  4. Tectorial membrane The tufts of the hair cells reach up to it. They bend when the basilar membrane moves.
  5. Inner hair cells They are the main sound receptors.
  6. Outer hair cells They fine-tune the response to a sound.

How this list was compiled: Every name and detail checked on 2026-09-30 against OpenStax Anatomy and Physiology 2e, section 14.1 Sensory Perception (audition: oval and round windows, scala vestibuli, cochlear duct, scala tympani, organ of Corti, basilar membrane, hair cells, tectorial membrane, spiral ganglia), https://openstax.org/books/anatomy-and-physiology-2e/pages/14-1-sensory-perception, and against Wikipedia, Cochlea and Organ of Corti, text only. The names OpenStax does not print were confirmed in Wikipedia and in a second text: inner and outer hair cells in OpenStax Biology 2e, section 36.4, https://openstax.org/books/biology-2e/pages/36-4-hearing-and-vestibular-sensation; helicotrema, modiolus and vestibular membrane in Gray, Anatomy of the Human Body, 20th edition, 1918 (public domain), https://archive.org/details/anatomyofhumanbo00grayrich, and in TeachMeAnatomy, The Inner Ear, https://teachmeanatomy.info/head/organs/ear/inner-ear/. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work

How it works

The cochlea is a coiled tube with three fluid-filled chambers. Four drawings take it apart: uncoiled, cut through its turns, one turn enlarged, and the organ of Corti, where hair cells turn sound into nerve signals.

Read the full guide

Four drawings, from the whole tube to a hair cell

Numbers 1 to 6 are on the cochlea drawn uncoiled: the scala vestibuli from the oval window to the helicotrema at the tip, the scala tympani back to the round window, and the cochlear duct between them. Numbers 7 to 9 are in the cut through the turns: the modiolus, the spiral ganglion and the cochlear nerve. Numbers 10 and 11 are in one turn enlarged, and 12 to 15 in the organ of Corti.

  • The scala vestibuli is continuous with the vestibule, at the oval window; the scala tympani ends at the round window.
  • High notes move the basilar membrane near the base of the cochlea; low notes move it near the tip.

Questions and answers

What are the three chambers of the cochlea?

The scala vestibuli, the cochlear duct (scala media) and the scala tympani. The two scalae hold perilymph and join at the helicotrema. The cochlear duct lies between them, holds endolymph and carries the organ of Corti.

What is the organ of Corti?

The organ of Corti, or spiral organ, is the strip of cells on the basilar membrane that senses sound. It has one row of inner hair cells and three rows of outer hair cells, under the tectorial membrane.

What does the basilar membrane do?

It forms the floor of the cochlear duct and carries the organ of Corti. Waves in the fluid move it at a spot that depends on the pitch, and that movement bends the tufts of the hair cells against the tectorial membrane.

What is the helicotrema?

The opening at the tip of the cochlea where the scala vestibuli and the scala tympani join. Fluid pushed in at the oval window can move through it and out toward the round window.

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