Learn about the structure and function of the human circulatory system, which consists of the heart, blood vessels, and blood. See diagrams of the heart, lungs, coronary system, and systemic circulation. The human circulatory system is a complex system consisting of different types of tissues. The main organ of the human circulatory system is the heart which pumps blood throughout the body. The human circulatory system also consists of a vast network of vessels or pipelines that carry blood throughout the body. The cardiovascular system includes the heart and blood vessels. This article covers normal and abnormal circulatory system function. Learn how the circulatory system transports blood, gases, nutrients and waste products throughout the body. See the diagram of the heart, arteries, veins and capillaries, and how they work together in double circulation.