Overview
This lecture explains the structure of the cochlea, focusing on its main parts and how it converts sound vibrations into nerve signals.
Cochlea Structure
- The cochlea is a spiral-shaped, fluid-filled structure in the inner ear.
- It contains three main fluid-filled areas: scala vestibuli (top), cochlear duct (middle), and scala tympani (bottom).
- The cochlear duct is also called the scala media.
Key Membranes and Areas
- The vestibular (Reissner's) membrane separates the scala vestibuli and the cochlear duct.
- The basilar membrane separates the cochlear duct from the scala tympani.
- The organ of Corti, located within the cochlear duct, contains hair cells and is the main sensory organ for hearing.
Hair Cells and Sound Transmission
- Hair cells in the organ of Corti have tiny projections called stereocilia.
- The stapes bone at the oval window sends vibrations through the cochlear fluid.
- Vibrations move the tectorial membrane, bending the hair cells' stereocilia and generating nerve signals.
- These nerve signals travel through the cochlear nerve to the brain.
Key Terms & Definitions
- Cochlea — spiral, fluid-filled structure in the inner ear responsible for hearing.
- Scala Vestibuli — upper fluid-filled chamber in the cochlea.
- Cochlear Duct (Scala Media) — middle chamber containing the organ of Corti.
- Scala Tympani — lower fluid-filled chamber.
- Vestibular (Reissner's) Membrane — membrane dividing scala vestibuli and cochlear duct.
- Basilar Membrane — membrane separating cochlear duct and scala tympani, supports the organ of Corti.
- Organ of Corti — sensory structure in the cochlear duct housing hair cells.
- Hair Cells — sensory cells with stereocilia that detect sound vibrations.
- Stereocilia — small hair-like projections on hair cells.
- Cochlear Nerve — nerve carrying hearing signals to the brain.
Action Items / Next Steps
- Review the structure and labeling of the cochlea.
- Learn the function of each cochlear region and membrane.