How do epithelial cells obtain their nourishment and remove waste products?

• A. By active transport from the surface
• B. By diffusion from underlying connective tissue
• C. By direct absorption from the external environment
• D. Through their own blood vessels

Answer: (B)

Verified step by step guidance

1. Understand the structure and function of epithelial tissue: Epithelial cells form a protective layer that covers surfaces and lines cavities in the body. They are avascular, meaning they lack their own blood vessels.
2. Recognize the role of connective tissue: Beneath epithelial tissue lies connective tissue, which contains blood vessels. These blood vessels supply nutrients and remove waste products for the epithelial cells.
3. Learn the process of diffusion: Diffusion is the passive movement of molecules from an area of higher concentration to an area of lower concentration. Nutrients and waste products move between the epithelial cells and the blood vessels in the connective tissue via diffusion.
4. Eliminate incorrect options: Active transport from the surface is not applicable because epithelial cells rely on diffusion, not active transport, for nourishment. Direct absorption from the external environment is incorrect because epithelial cells are not directly exposed to blood vessels or external sources. The option 'through their own blood vessels' is incorrect because epithelial cells are avascular.
5. Conclude that epithelial cells obtain their nourishment and remove waste products by diffusion from the underlying connective tissue, which is supported by the presence of blood vessels in the connective tissue.