Thirteen blood facts to absorb

"Why do we have different blood types?" asks Doug from Norfolk in The Curious Cases of Rutherford & Fry. This enquiry prompts science sleuths Hannah Fry and Adam Rutherford to discover these fabulous facts about blood.

1. You have around 30 TRILLION red blood cells.

They make up a quarter of the total number of cells in your body.

2. In its 3-4 month lifespan, each blood cell will make 150,000 LAPS around your body.

3. Your body produces TWO MILLION new red blood cells EVERY SECOND to replace those that have died.

4. Dead red blood cells help make poo brown.

5. There are over 30 minor blood groups…

6. But the two major groups tested for are the ABO group and Rhesus positive or negative.

7. The first recorded successful human blood transfusion was performed in 1818 by British obstetrician James Blundell.

The patient was a haemorrhaging woman who had just given birth. Blundell took blood from her husband’s arm and inserted it using a syringe. She lived to tell the tale, as did half of his patients. Those that died are thought to have been due to incompatible blood types.

8. Blood can be rejected by your body if it’s the wrong group.

The ABO system represents different proteins that are stuck to the outside of your red blood cells. You can either have A, B, both (AB) or none (O). If someone who is type A receives type B blood, then their body tries to attack the foreign B protein.

9. If you are AB blood type you are a “universal recipient”.

Because you have both A and B, your body can receive any combination of these proteins in transfused blood.

10. If you are blood type O you are a “universal donor”.

Type O blood does not contain any “foreign invader” that would result in rejection. This is the type of blood kept in A&E departments and air ambulances, when there isn’t time to test blood type before transfusions.

11. People with type O blood are less likely to suffer from deep vein thrombosis.

12. Rhesus is another type of protein on the outside of red blood cells.

If you have it you are Rhesus positive. If not, you are Rhesus negative.

Pregnant women are screened to see if they are Rhesus negative. If their baby is Rhesus positive, and any blood is mixed during birth, then the mother may mount an immune reaction and produce antibodies which could harm subsequent pregnancies. This is known as the Blue Baby Syndrome. But nowadays we screen for Rhesus factor, and if necessary antibiotics are given to block the mother’s immune reaction to protect future embryos.

13. Some of the minor blood groups have their own evolutionary advantages.

For example, if you are "Duffy negative" you are naturally more resistant to malaria. In West Africa, over 95% of the population have inherited this helpful trait.