Stereocilia are very long microvilli found in which locations?

• A. Lungs
• B. Epididymis (for absorption) and inner ear
• C. Kidney ducts
• D. Intestine

Answer: (B)

Stereocilia are exceptionally long microvilli that extend from certain epithelial cells to boost surface area for absorption or to act as highly specialized sensory projections. In the epididymis, these tall, nonmotile extensions maximize the reabsorption of fluids and proteins as sperm mature. In the inner ear, they form the tall hair-like bundles on sensory hair cells that bend with sound vibrations to convert mechanical stimuli into neural signals. That combination of location and function is why this is the best answer: stereocilia are not just any microvilli, but long, specialized ones found in these two sites.

In the lungs, the surface features are primarily cilia and standard microvilli are not described as stereocilia. The kidneys and intestines rely on the usual brush-border microvilli for absorption and do not feature the very long stereocilia characteristic of the epididymis and inner ear.