What is the Difference Between Endolymph and Perilymph?

Endolymph and perilymph are two distinct fluids found within the inner ear, playing crucial roles in hearing and external sound transduction. The main differences between endolymph and perilymph are their chemical compositions and locations within the inner ear:

1. Chemical Composition: Endolymph has a composition similar to intracellular fluids, with high potassium (K+) and low sodium (Na+) concentrations. Perilymph, on the other hand, has a composition similar to extracellular fluids, with high sodium and low potassium concentrations.
2. Location: Endolymph is located within the membranous labyrinth of the inner ear, specifically in the scala media. Perilymph fills the space inside the bony labyrinth, which surrounds the membranous labyrinth, and is found within the scala tympani and scala vestibuli of the cochlea.
3. Ionic Concentrations: Endolymph has a potassium concentration of about 150 mM and a sodium concentration of about 1 mM, while perilymph has a sodium concentration of about 150 mM and a potassium concentration of about 5 mM.
4. Protein Content: Perilymph contains a large number of proteins, such as extracellular enzymes and immunoglobulins, which are important for immune responses and metabolism. Endolymph does not contain as many proteins as perilymph.

Both endolymph and perilymph play vital roles in the functioning of the inner ear, and disruptions in their functions can lead to diseases such as Ménière's disease.

Comparative Table: Endolymph vs Perilymph

Here is a table comparing the differences between endolymph and perilymph:

Both endolymph and perilymph are physiological fluids found in the inner ear and play a pivotal role in external sound transduction to the brain. Disruptions in their functions can lead to diseases such as Ménière's disease.