Final answer:
Veins serve as the blood reservoirs of the body because they can hold large volumes of blood, which can be redistributed as needed. They have thinner walls compared to arteries, allowing them to expand and store blood, and they are equipped with valves to prevent backflow.
Step-by-step explanation:
The vessels that serve as the blood reservoirs of the body are the veins. Veins are crucial for storing large volumes of blood, which can be redistributed to other parts of the body as needed. Unlike arteries, which have thicker walls to handle high pressure and are active in the circulation of oxygen-rich blood away from the heart, veins have thinner walls and can accommodate a larger volume of blood, serving as reservoirs. They are equipped with valves that help maintain the direction of blood flow back to the heart, especially in the lower limbs against gravity. Additionally, the skeletal muscle action around veins helps in propelling the blood towards the heart.
Veins can expand to store extra blood due to their compliant walls. This capacity to store various blood volumes makes them act as a reservoir, meaning that during times when the body is at rest or the demand for blood is lower, veins can hold more blood. When the body becomes more active and requires more blood and oxygen, this stored blood can be efficiently redistributed to the areas in need.