Final answer:
The cross-sectional area of the aorta is larger than that of the capillaries. As blood flows from the aorta to the capillaries, it branches into smaller arteries, increasing the total cross-sectional area. This branching reduces the average velocity of the blood.
Step-by-step explanation:
When blood flows through the circulatory system, it passes through different types of blood vessels, including the aorta and capillaries. The aorta is a major artery with a larger cross-sectional area compared to the capillaries. As blood moves from the aorta to the capillaries, it branches into smaller arteries, increasing the total cross-sectional area. This branching reduces the average velocity of the blood. The reduced velocity in the capillaries allows for the exchange of substances with the surrounding cells.