Which fluid is contained within the scala media?

The fluid contained within the scala media is endolymph. This specialized fluid is critical for the function of the inner ear, particularly in the context of hearing and balance. The scala media is one of the three chambers of the cochlea, which is part of the inner ear. It is the site where the hair cells, responsible for converting sound vibrations into neural signals, are located. Endolymph has a unique ionic composition, which is crucial for the proper functioning of these sensory cells, as it helps to create the electrochemical gradients necessary for signal transduction.

In contrast, perilymph is found in the scala vestibuli and scala tympani, which lie outside the scala media, and serves a different role. Synovial fluid is a lubricant found within joints, and cerebrospinal fluid surrounds the brain and spinal cord, neither of which is relevant to the cochlear structure. Thus, endolymph is specifically the fluid associated with the scala media, highlighting its importance in auditory physiology.