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Blood types

The blood is composed of both red blood cells and white plus platelets. Thus, the blood group of each person is identified by the antibodies and antigens present in the blood. Antibodies are a type of protein present in plasma; They are part of the natural defenses of the immune system . For their part, antigens are protein molecules found on the surface of red blood cells.

It is estimated that in the case of adults, between five and six liters of blood circulate through the veins . One of the main functions of the blood is to serve as a means of transport for the cells of the immune system. Its speed of movement is very fast, so the transfusion is essential to treat certain medical conditions. Thus, in the same way that occurs with organ donation and transplantation, there are a series of requirements to assess.

Components of blood

Blood is a substance that is made up of four elements.

  • Red blood cells : better known as red blood cells, their main function is to transport oxygen from the lungs to the rest of the body. They are also responsible for transporting carbon dioxide from the cells to the lungs for later elimination.
  • Leukocytes: also called white blood cells, they are a group of cells that play a leading role in the immune system. They protect you against any type of external aggression.
  • Platelets: cell fragments that circulate in the bloodstream. Its main function is that of coagulation, as well as the healing of any type of break that occurs in the blood vessels.
  • Plasma: it is the liquid part of the blood and practically 100% of its composition is water and proteins. It is a means of transport and plays a very important role in the defense of the immune system, as well as in coagulation.

The different types of blood

When establishing the different types of blood that exist, attention is paid to two systems AB0 and Rh.

AB0 system

This system is made up of a total of four blood types A, B, AB, and o. Thus, people with type A have antibodies in their blood against type B. While, people with type B have antibodies in their bloodstream against type A. Those with type AB blood do not have antibodies. And finally, people with type O have both anti-A and anti-B antibodies.

Rh system

Starting from the four blood groups established by the ABo system, the Rh system establishes two blood types: + and – .

AB0 and RH classification for blood types

Taking into account the considerations explained in the previous point, eight different types of blood are differentiated.

Group A

It only has antigen A in red blood cells, as well as antibody B in plasma.

A +

You can donate: A + and AB +

You can receive from: A ± and O ±


You can donate: A ± and AB ±

You can receive from: A- and O-

B Group

Blood group B is characterized by having the B antigen on red blood cells, in addition to an antibody in the plasma.

B +

You can donate: B + and AB +

You can receive from: B ± and O ±.


You can donate: B ± and AB ±

You can receive from: B- and O-

AB Group

This blood group is characterized by having A and B antigens on red blood cells. However, you do not have A or B antibody in your plasma.

AB +

You can donate: AB +

Can receive from: universal receiver


You can donate: AB ±

You can receive from: A-, B-, AB- and O-

Group 0

It does not have A or B antigens on red blood cells, although in this case antibodies A and B are found in plasma.

O +

You can donate: A +, B +, AB + and O +

You can receive from: O ±


You can donate: universal donor

You can receive from: O-

Curiosities about the different blood types

Next we are going to answer some of the questions that are most commonly asked about the different blood types.

What is the most common blood type?

Currently, O + is the most common blood type globally ; studies indicate that about 50% of the world’s population has it. As the Red Cross indicates, about 37% of Caucasian people have the O + blood type; the percentage increases to 47% for African-Americans.

The second place in the ranking is for blood type A + . And, the third for B + .

What is the rarest blood type?

Another of the most frequently asked questions about this topic. Well, it is considered that the types AB and O are the blood types that occur less frequently.

The truth is that those patients with O- blood have it very difficult to find compatible donors for two reasons. For one thing, they can only receive blood from the same group. And, on the other hand, only 5% of the world’s population has this type of blood.

You may also be interested in:   Erythrosedimentation

Why is blood type so important?

The immune system develops certain types of proteins called antibodies. Well, the main function of these is to protect the body from invading cells that enter it. In this way, depending on the type of blood that each person has, the immune system will be responsible for the manufacture of certain antibodies, which react to other types of blood.

Thus, if during a transfusion a patient is administered a different type of blood than his, the organism will respond aggressively, putting the patient’s life at serious risk. The most common symptoms are fever , hypotension, and chills.

Thus, if a patient has blood group A, this implies that their blood produces antibodies B. Thus, if the transfusion is performed incorrectly and blood from people with type B or AB is administered, type B markers will enter. in your body. In this way, the immune system will react against them.

Universal donors and recipients

Those with type O negative blood are universal donors . It does not present any type of marker that can trigger an immune system reaction. That is why these types of donors are the most appreciated by blood banks.

Similarly, patients whose blood is type AB + have all the markers. Therefore, they can receive any type of blood. They are known as universal receivers.

Blood transfusions

Blood transfusions are a relatively common medical procedure. In it, a certain patient receives blood, either whole or one of its specific components, intravenously.

Thus, in general terms, a blood transfusion has as its main objective to replace a loss of blood , or of some of its components, in the recipient patient. Although there are whole blood transfusions, the truth is that it is not a very frequent procedure. In the vast majority of cases, specific blood components are transfused, such as plasma or red blood cells.

In relation to the duration of this type of transfusion, it ranges from one to four hours, depending on a series of factors such as the amount of blood or the blood group, among others.


For several centuries the medical community has been totally oblivious to the functions of the blood. Although it is true that doctors intuited its importance and numerous attempts were made at blood transfusions to deal with different diseases, in the vast majority of cases they were harmful to patients.

It was at the beginning of the 20th century that the German pathologist Karl Landsteiner began combining blood from different patients. He was the first to determine that some mixes were compatible, while others were not.

Karl Landsteiner discovered that on the surface of the red blood cells , there were two types of antigens: A and B. In addition, he observed that two types of antibodies were also found in the blood plasma that generated a reaction to the proteins of the red blood cells; He called them Anti-A and Anti-B.

The continuations of the doctor continued until the middle of the 20th century, when the compatibility of the Rh and ABo factors was established.

Causes of blood transfusions

Here are some of the most common causes of blood transfusion.

  • Loss of blood in the recipient patient, due for example to a certain operation or a serious injury.
  • Inability to produce enough blood due to illness / or treatment. For example, chemotherapy dramatically reduces the body’s production of new blood cells.


The procedure is relatively simple and fast.

The first fundamental step is to determine the blood group. To do this, a nurse takes a blood sample, which is subsequently identified and sent to the blood bank laboratory.

Once the blood group is known, it is time to select a compatible donated blood. As a final check, the laboratory technician mixes a small sample of both bloods to determine whether or not they are compatible.

And finally, a nurse places an IV in the arm or hand, to which the bag containing the blood is connected to perform the transfusion.


Ultimately, blood types are defined by a set of characteristics that are located on the surface of erythrocytes. It is important for each person what the blood group is. Similarly, donating blood is essential as it saves lives.

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Hello Readers, I am Nikki Bella a Psychology student. I have always been concerned about human behavior and the mental processes that lead us to act and think the way we do. My collaboration as an editor in the psychology area of ​​Well Being Pole has allowed me to investigate further and expand my knowledge in the field of mental health; I have also acquired great knowledge about physical health and well-being, two fundamental bases that are directly related and are part of all mental health.

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