What is the primary composition of perilymph in the inner ear?

The primary composition of perilymph in the inner ear is akin to blood plasma, which is why that choice is the correct one. Perilymph is an extracellular fluid that surrounds the structures of the inner ear, specifically the cochlea, vestibule, and semicircular canals. Its composition is characterized by a high sodium concentration and low potassium concentration, which is similar to that of blood plasma.

This distinctive similarity to plasma plays a crucial role in ensuring proper ionic balance and fluid environment necessary for the function of hair cells in the cochlea, which are responsible for converting sound vibrations into neural signals.

Other choices, such as perilymph being the same as cerebrospinal fluid or rich in potassium, do not accurately reflect the true composition of this fluid. Furthermore, the suggestion that perilymph is only found in the cochlea is incorrect because it is present in the entire inner ear, surrounding both the cochlea and the vestibular apparatus. Understanding the specific makeup of perilymph is essential because it highlights the intricate balance of fluids and ions required for auditory and vestibular functions.