Exchange of gases and nutrients occurs by diffusion between the __________.

• A. arterioles and tissue cells
• B. artery walls and tissue cells
• C. arterioles and venules
• D. arteries and veins
• E. capillaries and tissue cells

Answer: (E)

Verified step by step guidance

1. Understand the role of capillaries in the circulatory system. Capillaries are small blood vessels where the exchange of gases, nutrients, and waste products occurs between the blood and tissue cells.
2. Recognize that capillaries have thin walls, consisting of a single layer of endothelial cells, which facilitates the diffusion process.
3. Identify the process of diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration. This is how oxygen and nutrients move from the blood in the capillaries to the tissue cells.
4. Consider the structure of the circulatory system: arteries carry blood away from the heart, arterioles are smaller branches of arteries, and capillaries connect arterioles to venules, which then lead to veins that return blood to the heart.
5. Conclude that the exchange of gases and nutrients primarily occurs at the capillary level, where the blood is in close proximity to tissue cells, allowing for efficient diffusion.