The arrow in the top left of the image is pointing to which feature?

• A. The basement membrane
• B. The nucleus
• C. The mitochondrion
• D. The ribosome

Answer: (A)

Recognizing tissue organization and boundaries is essential. The line the arrow points to is the basement membrane, the extracellular matrix that anchors the epithelium to the underlying connective tissue. On a light-microscope slide stained with H&E, it appears as a thin, dense line just below the epithelial cells, marking the boundary between the two tissue types. It is not a cell and does not contain a nucleus, mitochondria, or ribosomes. Organelles like mitochondria and ribosomes are intracellular and typically not visible as distinct structures in routine light microscopy, whereas the nucleus belongs inside cells. So the boundary line corresponds to the basement membrane.