A Level Biology Practice Exam

What role do veins play in the circulatory system?

1. They distribute oxygenated blood from the heart to the rest of the body

2. They carry blood back to the heart

3. They facilitate gas exchange in lung tissue

4. They connect arteries to capillaries

The correct answer is: They carry blood back to the heart

Veins are a crucial component of the circulatory system, primarily tasked with the function of returning deoxygenated blood from various parts of the body back to the heart. This process is essential for maintaining proper circulation, as it allows the heart to pump blood to the lungs for oxygenation. As blood travels through the body, it delivers essential nutrients and oxygen to tissues, and after acquiring carbon dioxide and metabolic wastes, it is collected by veins. While arteries are responsible for distributing oxygenated blood away from the heart, veins take on the opposite role, ensuring that blood cycles efficiently through the circulatory system. They operate under lower pressure compared to arteries and contain one-way valves that prevent the backflow of blood, thus facilitating its return to the heart. Other options address different functions or types of blood vessels; however, they do not accurately describe the specific role of veins.