The circulatory system consists of three independent systems that work together: the heart (cardiovascular), lungs (pulmonary), and arteries, veins, coronary and portal vessels (systemic). The system is responsible for the flow of blood, nutrients, oxygen and other gases, and as well as hormones to and from cells.
carbon-With four electrons that can be shared to make covalent bonds, carbon-based molecules display an enormous variety of size, shape, and properties.
