Circulatory system - structure, functions
Structure of the circulatory system The human circulatory system consists of the HEART pumping blood and the BLOOD VESSELS responsible for transporting blood throughout the body. It is a closed system, because blood doesn't leak out into the body cavities. SOURCE Arteries • They transport blood from the HEART to all BODY CELLS. Their walls are made of layers that expand and contract with the beating of the heart. • Arteries are elastic and this is due to the presence of a large number of elastic fibers in their structure. Thick, resilient and flexible walls withstand the high blood pressure. • The arteries never collapse. The blood flowing through the arteries is light in color , this is due to the high oxygen content (the exception is the pulmonary artery through which deoxygenated blood flows) Veins • They transport blood from the BODY CELLS to the HEART . Their walls, like the walls of arteries, are made of layers, but much thinner. • Veins can collapse. In the veins, t
