What is blood made up of?
Simply put, blood is a fluid that circulates around your body, performing important functions to keep you alive. Blood contains plasma, cells and proteins, thus the saying “blood is thicker than water”, and a person of average build has about 5-litres of blood in his body.
Plasma which contains proteins, glucose, and nutrients among things, makes up about half of the blood’s content. The proteins are important as they help blood to clot when there is a cut on the skin surface.
The rest of blood volume has:
- red blood cells which carry oxygen to body tissues
- white blood cells which flight infections
- platelets which are tiny blood cells that help form clots to stop bleeding
Blood travels throughout the human body via a vast complicated network of arteries and veins.
Is your blood type A, B, AB, or O (the letters and pluses and minuses indicate different blood types)? Many people know the type of blood they have, but not much apart from that which can be crucial in an emergency, especially if you urgently need a blood transfusion.
In the early 1800s, only half of patients who received blood transfusions survived. It was only after Austrian immunologist and Nobel Prize winner, Dr Karl Landsteiner, discovered blood types in 1901, that scientists learned humans should only get blood from certain other humans.
Your ABO blood group is identified by antibodies which are part of the body’s defence system, and antigens which are a combination of sugars and proteins that coat the surface of red blood cells. During a blood transfusion, your antibodies will recognize foreign antigens from another blood group and alert your immune system to destroy them, hence giving a patient blood from the wrong group can be a matter of life or death.
Another important discovery made by Dr Landsteiner is blood types are inherited from parents. Blood types are determined by an “Rh” status, which is an inherited protein found on the surface of red blood cells. If you have it, you’re classified as Rh positive, if you don’t have it, you are classified as Rh negative.
Rh positive people can accept blood from positive or negative blood types.
Rh negative people can only accept blood with Rh negative blood types.
This means there are 8 possible primary blood types, and there are a few more rare blood types – A+, A-, B+, B-, AB+, AB-, O+ and O-.
Blood type A has only the A antigen on red cells and B antibody in the plasma.
Blood type B has only the B antigen on red cells and A antibody in the plasma.
Blood type AB has both A and B antigens on red cells, but none in the plasma.
Blood type O has no A nor B antigens on red cells but both are in the plasma.
How is blood type determined?
As mentioned earlier, Dr Landsteiner discovered blood types are inherited from both parents.
The following chart shows what types of blood types are compatible for blood transfusions. A point to note here is O- blood can be used for any blood transfusion.
Universal blood donor
Universal blood donors are classified as those with O- blood, since O- can be used in any blood transfusions.
Rare blood types
The American Red Cross states that the presence or absence of more than 600 other known antigens determines rare blood types. In other words, people with rare blood types are those whose blood lacks antigens that 99% of people are positive for. If a person lacks an antigen that 99.99% of people are positive for, you have an extremely rare blood type.
We hope this article has given readers an insight into blood and blood types. Any part of this article should not be taken as medical advice, and readers are advised to consult their doctors for detailed information on blood issues.
20th July 19:00 2020