A circulatory system is a network that transports blood, nutrients, gases, and waste products throughout an organism's body. In humans and many animals, this system consists of the heart, blood vessels, and blood. The heart pumps blood through arteries, veins, and capillaries, ensuring that oxygen and nutrients reach cells while removing carbon dioxide and other waste. There are two main types of circulatory systems: open and closed. In an open circulatory system, like that of insects, blood flows freely within body cavities. In contrast, a closed circulatory system, found in humans and mammals, keeps blood contained within vessels, allowing for more efficient transport and regulation.