The tissue components stained black in the image are which of the following?

• A. Basement membrane
• B. Myelin
• C. Collagen
• D. Muscle

Answer: (A)

Basement membranes stain black on many silver-based stains because they are rich in carbohydrate-containing matrix components that readily take up and deposit metallic silver. This creates a sharp, continuous dark line separating epithelium from underlying connective tissue, which is a hallmark of basement membrane Under silver impregnation techniques, the basement membrane (and sometimes reticular fibers) appears intensely dark, making it the easiest structure to identify in many stained sections.

Myelin would be highlighted by other stains specific for neural tissue, not as a thin, continuous black line around epithelial structures. Collagen typically appears blue or green with trichrome methods or red with certain stains, not black. Muscle fibers usually stain pink to red with routine stains and do not form that distinct dark boundary seen with basement membranes in silver stains.