Which tissue component is blue in the described image?

• A. Skeletal muscle
• B. Collagen
• C. Nuclei
• D. Elastic fibers

Answer: (A)

Color in tissue sections comes from how the stain binds to different cellular components. In this image, the blue color is taking up the muscle fibers themselves, which is how this particular staining method highlights skeletal muscle. The elongated, fiber-shaped units you see with a uniform blue cytoplasm correspond to skeletal muscle, whose structure is distinct from the other components.

Why this is the best fit: the appearance matches the morphology of skeletal muscle—long, cylindrical fibers with consistent staining throughout the fiber. The other options would present differently: collagen would form an extracellular, fibrous network often seen surrounding cells and not filling the entire muscle fiber; nuclei would appear as discrete small blue/purple spots within cells rather than the entire fiber; elastic fibers are thin, threadlike elements that stain darkly and do not constitute the bulk of the blue-colored structure shown.