Which of the following chambers of the cochlea is filled with a fluid similar to intracellular fluid with high K+ and low Na+?
**Core Concept**
The **cochlea** is a critical structure in the auditory system, responsible for sound processing and conversion into electrical signals. The cochlea contains two main fluid-filled chambers: the **scala vestibuli** and **scala tympani**, and the **scala media**. Each chamber has distinct ionic compositions.
**Why the Correct Answer is Right**
The correct answer is related to the ionic composition of the **scala media**, also known as the cochlear duct. This chamber is filled with a fluid called **endolymph**, which has a unique ionic composition similar to intracellular fluid, with high **potassium (K+)** and low **sodium (Na+)** concentrations. This ionic environment is crucial for the function of **hair cells** in the cochlea.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the scala vestibuli and scala tympani are filled with **perilymph**, which has a high Na+ and low K+ concentration.
**Option B:** This option is also incorrect as it does not match the description of the scala media.
**Option D:** This option does not correspond to the chamber with the described ionic composition.
**Clinical Pearl / High-Yield Fact**
The unique ionic composition of the endolymph in the scala media is essential for the proper functioning of the cochlea, and disturbances in this environment can lead to hearing impairments.
**Correct Answer:** C. Scala media.