What is the basic function of veins in the cardiovascular system?

The basic function of veins in the cardiovascular system is to transport deoxygenated blood back to the heart. After oxygen is delivered to the tissues through the arteries, blood returns to the heart via the veins. This process is crucial for the correct functioning of the circulatory system, as it allows for the removal of carbon dioxide and other metabolic waste products from the body's tissues. Veins have thinner walls and larger lumens compared to arteries, which helps facilitate the return of blood at lower pressure.

While arteries carry oxygenated blood away from the heart, veins specifically play the role of returning deoxygenated blood. The other options describe processes or functions not directly associated with the primary role of veins in blood circulation. Nutrient absorption takes place in the gastrointestinal tract, and hormonal regulation involves various systems throughout the body, but neither are functions of veins in the context of blood circulation.