Which statement correctly identifies the two primary characteristics of epithelium?

• A. It has a rich blood supply.
• B. It is avascular and has a free surface.
• C. It is non-vascular and has a basement membrane.
• D. It contains nerve tissue throughout.

Answer: (B)

Epithelial tissue is avascular and has a free surface. It contains no blood vessels, so nutrients and oxygen must diffuse from vessels in the underlying connective tissue across the basement membrane to reach the epithelial cells. The free/apical surface faces a lumen or the external environment, giving the tissue its exposed side for protective, absorptive, or secretory roles. The basement membrane anchors the epithelium to the underlying tissue and helps regulate exchange, but the most defining pair described here is its lack of blood vessels and its exposed surface. The other statements are not the typical defining pair: a rich blood supply would contradict avascularity, and while nerves exist nearby, epithelium itself isn’t a tissue rich in nerve fibers throughout.