Blood

The blood performs three major functions: (1) transport through the body, (2) regulation of bulk equilibria, and (3) body immune defense against foreign bodies. It supplies oxygen, and hence energy, and conveys nutrients (vitamins, mineral ions, glucose, amino acids, fatty acids among other glucids, protids, and lipids) to the tissues and removes carbon dioxide and waste products of cell metabolisms toward lungs and purification organs. The kidneys filter the blood. Toxins are not only removed in urine but also by sweating. The blood transmits metabolism factors and messengers, such as hormones, to the target organs. Blood volume and electrolyte concentration are regulated. Blood maintains the body temperature (36.4–37.1 °C) and acid—base equilibrium, controlling blood pH, which remains in the range 7.35 to 7.45. The blood is involved in the body defense against infection, transporting immune cells and antibodies, and in repair processes after injury. It limits blood losses by clotting (Sect. 9.4). The blood contains living cells and plasma (Table 6.1). Eight to twelve hours after a meal, 100 ml of blood contains 19 to 23 g of solids and 77 to 81 g of water.