The key difference between basilar and tectorial membrane is that basilar membrane is the membrane that forms the floor of the cochlear duct, on which the cochlear hair cells lie embedded, while tectorial membrane is the fibrous sheet overlying the apical surface of the cochlear hair cells.
Cochlea is a coiled structure found within the inner ear. It is the most critical structure in the auditory pathway. It amplifies sound waves and converts them into neural signals. Structurally, it is a spiral-shaped bone, which resembles a snail shell. It consists of three canals (the scala vestibuli, scala media, and scala tympani) that run parallel to one another. Moreover, it is filled with a fluid. There are two acellular membranes in the cochlea. They are basilar membrane and tectorial membrane. Auditory receptor cells lie on the basilar membrane while tectorial membrane lies over the auditory receptor cells or hair cells. Both basilar membrane and tectorial membrane are components of the organ of Corti.
CONTENTS
1. Overview and Key Difference
2. What is a Basilar Membrane
3. What is a Tectorial Membrane
4. Similarities Between Basilar and Tectorial Membrane
5. Side by Side Comparison – Basilar and Tectorial Membrane in Tabular Form
6. Summary
What is a Basilar Membrane?
Basialar membrane is one of the two acellular membranes located in the inner ear. This membrane forms the floor of the cochlear duct. Basilar membrane divides the spiraled cochlear into upper and lower chambers. The auditory receptor cells or hair cells lie embedded within the basilar membrane. Generally, in human inner ear cochlea, there are 3500 inner hair cells and 12,000 outer hair cells. They are organized along the basilar membrane according to their frequency response.
Figure 01: Basilar Membrane
The basilar membrane is widest and least stiff at the apex of the cochlea while it is narrowest and stiffest at the base. Different parts of the basilar membrane vibrate in response to sound. And, this is the key to the understanding of cochlear function.
What is a Tectorial Membrane?
The tectorial membrane is a fibrous sheet overlying the apical surface of the cochlear hair cells. Structurally, it is a gel-like structure containing 97% of water. Tips of the outer hair cells are attached directly to this membrane.
Figure 02: Tectorial Membrane
Moreover, the tectorial membrane is located above the spiral limbus and the spiral organ of Corti. Besides, it extends along the longitudinal length of the cochlea parallel to the basilar membrane. There are three zones of the tectorial membrane as limbal, middle and marginal zones. The limbal zone is the thinnest while the marginal zone is the thickest. Furthermore, the tectorial membrane is important for the healthy auditory function in mammals. It influences inner ear sensory cells by storing calcium ions.
What are the Similarities Between Basilar and Tectorial Membrane?
- Basilar and tectorial membranes are two acellular membranes in the cochlea of the inner ear.
- They belong to the organ of Corti of the cochlea.
- They lie parallel to each other.
- Basilar membrane moves relative to the tectorial membrane due to sound waves.
- Both, basilar and tectorial membrane are important for healthy auditory function in humans.
What is the Difference Between Basilar and Tectorial Membrane?
The basilar membrane is an acellular membrane on which the hair cells lie embedded while the tectorial membrane is a fibrous sheet overlying the apical surface of the cochlear hair cells. So, this is the key difference between basilar and tectorial membrane. Furthermore, another difference between basilar and tectorial membrane is that the hair cells or auditory receptor cells lie embedded within the basilar membrane, while the tectorial membrane lies over the hair cells.
Summary – Basilar vs Tectorial Membrane
Basilar and tectorial membrane are two acellular membranes in the cochlea of the inner ear. The auditory receptor cells lie embedded within the basilar membrane while the tectorial membrane overlies the apical surface of the cochlear hair cells. Thus, this is the key difference between basilar and tectorial membrane. Moreover, the basilar membrane forms the floor of the cochlear duct. Sound waves cause the basilar membrane to move relative to the tectorial membrane. Both, basilar and tectorial membrane are important for a healthy auditory function.
Reference:
1. Purves, Dale. “The Inner Ear.” Neuroscience. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. “Basilar Membrane.” Wikipedia, Wikimedia Foundation, 18 Dec. 2019, Available here.
Image Courtesy:
1. “Cochlea-crosssection” By !Original: OarihVector: Fred the Oyster – Own work based on: Cochlea-crosssection.png (CC BY-SA 3.0) via Commons Wikimedia
2. “Organ of corti” By Madhero88 – Own work (CC BY-SA 3.0) via Commons Wikimedia