The circulatory system transports blood throughout the body, carrying oxygen, nutrients, water, and removing waste. Working with the respiratory system, it regulates body temperature and provides protection from infection by carrying antibodies. The heart acts as a pump to circulate blood through arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart while veins return deoxygenated blood back to the heart. Capillaries connect arteries and veins and allow for exchange of oxygen and carbon dioxide in tissues.