Where does the exchange of nutrients with surrounding tissues occur?

The exchange of nutrients with surrounding tissues primarily occurs in capillaries due to their unique structural characteristics. Capillaries are the smallest and most numerous blood vessels in the body, designed specifically for the exchange of gases, nutrients, and waste products between blood and tissues.

Their walls are incredibly thin—typically just one cell layer thick—which allows for easy diffusion of substances like oxygen, carbon dioxide, glucose, and other nutrients. This thinness enhances the efficiency of nutrient and waste exchange, as substances can move in and out of the blood more readily compared to larger blood vessels.

Additionally, capillaries often form networks or beds that increase the surface area for exchange, making them well-suited for their role in systemic circulation, particularly in tissues where metabolic activity is high and the demand for nutrients and oxygen is elevated.

In contrast, arteries and veins primarily function to transport blood; arteries carry oxygenated blood away from the heart, while veins return deoxygenated blood to the heart. The heart itself is a muscular organ that pumps blood, but does not engage in nutrient exchange. Hence, the capillary network is the critical site for nutrient exchange in the circulatory system.