Blood

Blood has two components, plasma and cells. Plasma is the liquid part of the blood. it is made up of 90% water and the other 10% are materials that are essential for life. i.e. nutrients and vitamins - these are dissolved in the blood plasma.
The cell part of the blood contains RBC (Red blood cells), WBC (White blood cells) and platelets. The RBC consists of a protein called Hemoglobin which carries oxygen from the lungs around the body, they also help with the removal of carbon dioxide. When RBC are produced they contain a nucleus as the RBC matures the nucleus leaves the cell. The WBC fight infections, they are often referred to as Leukocytes. The WBC are part of the immune system and they circulate in the blood stream so that they can be transported to infected areas in the body. The platelets are used by the body for clotting.
as the blood circulates the body the materials that are in the plasma diffuse into cells and tissues. they diffuse from high concentrated areas too low concentrated areas (in other words the higher the difference in concentration the higher the amount of materials diffused.)


This is a picture to show what the platelets do when they begin to clot.