Learning Intentions

We are learning to....  Discover blood and what it is used for in our bodies

So that we can... Looking closely at blood typing 

We will be able to.... Work on  our CAT looking at whole blood, blood typing, and blood as evidence.

Blood is a specialized body fluid. It has four main parts: plasma, red blood cells, white blood cells, and platelets. The different functions of blood include:

• transporting oxygen and nutrients to the lungs and tissues

• forming blood clots to prevent excess blood loss

• carrying cells and antibodies that fight infection

• bringing waste products to the kidneys and liver, which filter and clean the blood

• regulating body temperature

The blood that runs through the veins, arteries, and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7 to 8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about nine pints.

Blood Types

When it comes to what blood type (or blood group) you have, it’s all about the antigens—the various sugars and proteins on the surface of our cells, including our blood cells. Which antigens you have or don’t have on your red blood cells determines your blood type. Antigens are genetically determined—inherited from a combination of your parents’ genes. 

There are two major systems for determining blood groups. The first is the ABO system based on antigens and antibodies. Antibodies fight substances in the body that are normally seen as foreign to the body. These substances are called antigens. The ABO system is based on the type of antigens you have on the surface of your red blood cells.

 For example, if you have A antigen present in your blood, then your blood group is A. Similarly, B antigen means blood group B. If both antigens are present, the blood group is AB. If neither is present, then it is blood group O.

 This blood grouping is also based on the antibodies present in the blood. For example blood group A has anti-B antibodies present. B blood has anti-A antibodies, AB has no antibodies and O has both antibodies. 

This is very important when blood transfusions are being given. Antigens and antibodies react together to produce clotting of the blood. So, a person with type A blood cannot be given type B blood because if the anti-B antibodies in the type A blood come in contact with B antigens in the type B blood, clotting will occur, destroying the red blood cells.