Blood id the fluid that is pumped around the body the circulatory system. Blood carries oxygen, which it picks up in the lungs. It distributes this oxygen to all body parts, since every body all needs a regular supply of oxygen to stay alive. Blood is made up of many components and has many functions. It consists of a yellow fluid, called plasma, in which red and white blood corpuscles and platelets are suspended. The capillaries allow fluid to escape from the blood. The cells and large proteins are left in the vessel and this fluid can now become the interstitial fluid (a background fluid that acts as an active support). This will either return to the capillary or join the lymphatic system. Blood amounts to about one – third of the total interstitial fluid.
The red white blood cells are formed in the bone marrow. The plasma occupies about 55 percent of the blood volume. It is 90 percent water, 7 percent proteins, with the remaining 3 percent made up of small molecules.