Every minute, each of your red blood cells completes its journey through the entire circulatory system, bringing oxygen to all cells, from your head to the little finger of the foot.
And every second your body produces two million red blood cells – or erythrocytes – that replace those that have already died.
1. You have about 30 billion red blood cells
The most abundant cells in your body are red blood cells. It is believed that there are about 26 billion in men and the figure is somewhat lower in women.
Platelets are also very abundant, although their number is much smaller.
In total, almost 90% of your body’s cells are found in the blood.
2. In its 3 or 4 months of life, each red blood cell makes 150,000 revolutions around your body
They run along a viscous “highway”, which are your veins and arteries at a speed of about 2 kilometers per hour.
3. Dead erythrocytes favor feces to be brown
Your body cannot simply discard “old” red blood cells because they have iron inside, very valuable for making more red blood cells to replace them.
Instead, some cells extract iron and generate bilirubin at the same time, which reaches the liver. This organ is excreted in the form of bile into the digestive system, where it is then transformed into a substance called urobilinogen and then stained.
4. There are more than 30 blood group systems
The four best known are A, B, AB and O, but there are many more.
In fact, “we know that there are 34 systems with more than 300 known variants,” Robert Flower, a professor at the University of Sydney in Australia, who works for the Red Cross Blood Bank , wrote for The Conversation .
“All of them are classified by the ‘antigens’, which are found on the surface of our red blood cells.”
“Antigens are molecules (most often proteins, but also carbohydrates) capable of causing our immune system to attack,” he added.
5. But the two main groups that are tested are the ABO and Rhesus positive or negative
The ABO test shows if the person has one of these four types of blood: A, B, AB or O.
The Rh test proves the existence of the Rh antigen (or factor).
Within these there are subgroups.
6. The first successful blood transfusion …
… was carried out in 1818 by British obstetrician James Blundell.
The patient was a woman with bleeding who had just given birth.
Blundell took blood from her husband’s arm and inserted it using a syringe. She lived to tell, as well as half of her patients. It is believed that those who died were from incompatible blood types.
7. Blood may be rejected by your body
After taking the ABO, you can turn out A, B, both (AB) or none (O).
If someone of type A receives type B blood, then their body will try to attack the foreign proteins of type B.
8. If you are AB, you are a “universal receiver”
Since you have A and B, your body can receive any combination of those two proteins in a blood transfusion.
9. If you are type O, you are a “universal donor”
Type O blood does not contain any “foreign invaders” that can result in rejection.
This is the type of blood that is stored in hospital emergency rooms and ambulances, when there is no time to test the blood type before making a transfusion.
10. If your blood group is O, you are less likely to suffer from deep vein thrombosis
It is a clot that causes pain and inflammation and can be dangerous.
It can happen to anyone at any time, but this type of blood determines that your risk is lower.
11. Rhesus (Rh) is another type of protein outside the red blood cells
The so-called “Rh factor” protein is inherited through genes.
If you have it, you are Rh positive. If you don’t have it, Rh negative.
Pregnant women are examined to see if they are Rh negative. If your baby is Rh positive and any type of blood is mixed during childbirth, then the mother can cause an immune reaction and produce antibodies, which could harm subsequent pregnancies because they remain in the body.
That is known as the blue baby syndrome.
Today it is detected if there is the so-called “Rh factor” and, if necessary, antibiotics are given to block the mother’s immune reaction and protect future embryos.
12. Some of the minority blood groups have their own evolutionary advantages
For example, if you have “Duffy negative” blood you are more resistant to malaria.
In West Africa, more than 95% of the population inherits that useful feature.