Infographic illustration showing the components of healthy blood. The two main components are plasma and red blood cells (erythrocytes). Red blood cells carry oxygen to body tissues and carbon dioxide to the lungs. Plasma is the fluid component of blood and is made up of water, proteins and various solutes. One percent of blood consists of platelets, cell fragments that promote blood clotting and wound healing, and white blood cells (leukocytes), which are the cells of the immune system.