Which vessels are primarily responsible for exchange of gases, nutrients, and wastes between blood and tissues?

Which vessels are primarily responsible for exchange of gases, nutrients, and wastes between blood and tissues?

• A. Arteries
• B. Veins
• C. Capillaries
• D. Aorta

Answer: (C)

Gas, nutrient, and waste exchange happens where blood is in closest contact with tissue cells. Capillaries are ideal for this because they form an extensive, thin-walled network right at the tissue level. Their walls are only a single layer of endothelial cells (often with a thin basement membrane), which allows molecules to diffuse or pass through via small pores or clefts. Oxygen and nutrients diffuse from blood into tissues, while carbon dioxide and other wastes diffuse from tissues into the blood to be carried away. Some capillaries even have specialized features—continuous, fenestrated, or sinusoidal—that tailor exchange to the needs of the tissue. Arteries and veins carry blood to and from tissues but are designed for transport under pressure, not for exchange. They have thicker walls and less surface area relative to capillaries, so diffusion across their walls is limited. The aorta, as a major artery, serves mainly for high-pressure blood transport rather than exchange.

Gas, nutrient, and waste exchange happens where blood is in closest contact with tissue cells. Capillaries are ideal for this because they form an extensive, thin-walled network right at the tissue level. Their walls are only a single layer of endothelial cells (often with a thin basement membrane), which allows molecules to diffuse or pass through via small pores or clefts. Oxygen and nutrients diffuse from blood into tissues, while carbon dioxide and other wastes diffuse from tissues into the blood to be carried away. Some capillaries even have specialized features—continuous, fenestrated, or sinusoidal—that tailor exchange to the needs of the tissue.

Arteries and veins carry blood to and from tissues but are designed for transport under pressure, not for exchange. They have thicker walls and less surface area relative to capillaries, so diffusion across their walls is limited. The aorta, as a major artery, serves mainly for high-pressure blood transport rather than exchange.