Your blood circulates throughout your whole body. It supplies food, oxygen, hormones, and other chemicals to all the body's cells. It also helps to remove waste products and is important in fighting infection and in controlling bleeding. Blood consists of 60% plasma (fluid) and 40% of blood cells. The three most important types of cells are red blood cells, white blood cells and platelets. Although we think of blood as a fluid, it is actually made up of both fluid and cells. These can be seen under a microscope.
Bone marrow is the "blood cell factory" which is found filling up the cavities of bones. All blood cells originate and are produced from a single "stem cell" whose progeny grow and mature into different types of blood cells. This stem cell can and does renew itself as required by our body.
Red blood cells (erythrocytes) carry oxygen from your lungs to all parts of your body. If you don't have enough red blood cells you have anemia.
Anemia can make you look pale and may make you feel tired, dizzy, irritable and short of breath. Red blood cells also pick up wastes on their way around the body, carrying them to the lungs to be breathed out as carbon dioxide.
White blood cells (leucocytes) are the body's infection fighters. There are three main groups of white blood cells: granulocytes, lymphocytes and monocytes. Their job is to rid your body of disease-causing bacteria, viruses, fungi and to destroy the body's dead or defective cells. If we do not have enough white blood cells we are at risk of catching all types of infections.
When the body is healthy, the numbers of red cells, white cells and platelets in the blood are kept in balance.