Difference Between Inner and Outer Hair Cells

The key difference between inner and outer hair cells is that the inner hair cells have much denser innervations while the outer hair cells have less dense innervations. Furthermore, the inner hair cells detect the sounds and send signals to the brain via the auditory nerve fibers while the outer hair cells involve in amplifying the sounds coming from the environments. Therefore, inner hair cells receive more afferent inputs than the outer hair cells.

Inner ear is one component of the ear. It has different components. Among them, hair cells are the receptive cells of it. These cells stretch along the cochlear duct in two rows. There are two types of hair cells; namely, inner hair cells and outer hair cells.

CONTENTS

1. Overview and Key Difference
2. What are Inner Hair Cells
3. What are Outer Hair Cells
4. Similarities Between Inner vs Outer Hair Cells
5. Side by Side Comparison – Inner vs Outer Hair Cells in Tabular Form
6. Summary

What are Inner Hair Cells?

Inner hair cells are a type of hair cells in the inner ear of the auditory system. These cells are much denser innervations than the other type called outer hair cells. Hence, inner hair cells are directly responsible for sending signals to the brain via the auditory nerve fibers.

However, they are less in number compared to outer hair cells. But more involves in the hearing. Because the auditory system receives afferent inputs from the inner hair cells than outer hair cells.

What are Outer Hair Cells?

Outer hair cells are the second type of hair cells in the inner ear. Compared to inner hair cells, outer hair cells are numerous in the ear. And they have less dense innervations.

Furthermore, they are not directly responsible for sending signals to the brain via auditory nerve fibers. Instead, they involve in amplifying the sounds.

What are the Similarities Between Inner and Outer Hair Cells?

• Inner and outer hair cells are sensory receptor cells in the inner ear.
• Both cell types cannot regenerate.
• Hair bundles protrude from the apical surface of both cell types.
• These cells can detect the movements in their environment.
• Damages to both inner and outer hair cells can result in hearing problems.

What is the Difference Between Inner and Outer Hair Cells?

Inner and outer hair cells are two types of receptor cells in the inner ear. Inner hair cells directly responsible for sending signals to the brain, on the other hand, outer hair cells involved in amplification of sounds. There are numerous outer hair cells than inner hair cells. Inner hair cells have dense innervations than outer hair cells. Furthermore, inner hair cells receive more afferent inputs than outer hair cells. The below infographic presents the important differences between inner and outer hair cells.

Summary – Inner vs Outer Hair Cells

Hair cells are the sensory receptor cells of the vertebrate auditory system. Inner and outer hair cells are two types of hair cells that are structurally and functionally distinct. They are located in the organ of Corti. Hair cells have cilia, and these cilia move when the organ of Corti moves. It creates a signal that goes via the auditory nerve fibers to the brain. Inner hair cells have much denser innervations than outer hair cells. Furthermore, the auditory system receives more afferent inputs via inner hair cells than from the outer hair cells. However, there are more outer hair cells in the inner ear than inner hair cells. This is the difference between inner and outer hair cells.

Reference:

1.“Hair Cell.” Wikipedia, Wikimedia Foundation, 7 July 2018. Available here  
2.“Inner and Outer Hair Cells.” Baylor College of Medicine. Available here  

Image Courtesy:

1.’Gray931’By Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below)Bartleby.com: Gray’s Anatomy, Plate 931, (Public Domain) via Commons Wikimedia 
2.’Outer hair cell and Deiter’s cell’By Inductiveload – Own work, (Public Domain) via Commons Wikimedia