The Life Drift into our Bodies

The blood is the life stream. It carries food and energy to all parts of the body; it scavenges the waste material of living which would otherwise poison the living creature; it helps to keep body temperature within the narrow limits in which cells can stay alive; it fights off the unceasing attacks of the bacteria of disease and decay. When the blood ceases to flow, life ends if the supply of blood to the brain stops for only a second, the person becomes unconscious.

Blood normally accounts for about 1/13th of a man's total weight. A man weighing 70 Kg has about 5.4 Kg of blood. Blood is pumped by the heart into the arteries which branch and become smaller and smaller , like the branches and twigs of a tree, into capillaries ( from Latin, ‘capillus' means a hair) The blood leaves the capillaries for minute veins which become bigger veins and returns to the lungs and heart to start its journey again.

What takes place When I give Blood?

A tiny drop of blood is taken from your fingertip. This allows us to check your haemoglobin levels and ensure that giving blood won't make you anaemic.

If all is well, you will be able to donate blood. You will donate about 470ml of blood - this amount of blood is quickly replaced by your body. Learn more about how the body replaces blood.

Once you have given blood, you should have a short rest before being given some refreshments usually a drink and biscuits. All in all giving blood shouldn't take more than an hour.

Blood Transfusion

Early experiments in replacing blood lost by one person with the blood of another seldom succeeded and sometimes proved fatal. Blood transfusion as a practical procedure began after it had been discovered that there are sharply different types or groups of blood. One classification recognized four types called for convenience A, B, AB and O. Between persons of the same blood type, blood can be exchanged safely. But where blood types differ, the following rules apply; persons of types A and B can receive blood from those of type AB: but persons of these first two types cannot exchange blood. Type AB can receive from persons of all other types (universal receivers), but can give to none outside their own group. Those of type B can receive from no other groups, but can give to all others (universal donors. The so called Rhesus factor (given that name because the experimental then work on clotting was done with Rhesus monkeys) is also important in blood transfusions. It may be dangerous to transfer Rhesus – positive blood to a Rhesus- negative person. The wrong type of blood introduced into a patient causes his red cells to clump and clot together blocking the capillaries and killing him.

Though experiments with blood transfusion, the transfer of blood or blood components into a person's blood stream, have been carried out for hundreds of years it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups , that blood transfusion became safer. Mixing blood from two individuals can lead to blood clumping or agglutination. The clumped red cells can crack and cause toxic reactions. This can have fatal consequences. Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells. Karl Landsteiner's work made it possible to determine blood types and thus paved the way for blood transfusions to be carried out safely. For this discovery he has awarded the Nobel Prize in Medicine in 1930.

Composition of blood

An adult human has about 4–6 liters of blood circulating in the body. Among other things, blood transports oxygen to various parts of the body.

Blood consists of several types of cells floating around in a fluid called plasma.

The red blood cells contain hemoglobin, a protein that binds oxygen. Red blood cells transport oxygen to, and remove carbon dioxide from, the body tissues.

The white blood cells fight infection.

The platelets help the blood to clot, if you get a wound for example.

The plasma contains salts and various kinds of proteins.

Types of blood groups?

The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules. The blood group you belong to depends on what you have inherited from your parents.

There are more than 20 genetically determined blood group systems known today, but the AB0 and Rh systems are the most important ones used for blood transfusions. Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.

Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.

AB0 blood grouping system

According to the AB0 blood typing system there are four different kinds of blood types: A, B, AB or 0 (null).

Blood group A

If you belong to the blood group A, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma

Blood group B

If you belong to the blood group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma

Blood group AB

If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma

Blood group 0

If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma

The Rh factor grouping

Rh factor blood grouping system Many people also have a so called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. According to above blood grouping systems, you can belong to either of following 8 blood groups:

A Rh+ B Rh+ AB Rh+ 0 Rh+

A Rh- B Rh- AB Rh- 0 Rh-

Do you know which blood group you belong to?

How do we detect the blood group of a sample?

  1. 1. You mix the blood with three different reagents including either of the three different antibodies, A, B or Rh antibodies.
  2. 2. Then you take a look at what has happened. In which mixtures has agglutination occurred? The agglutination indicates that the blood has reacted with a certain antibody and therefore is not compatible with blood containing that kind of antibody. If the blood does not agglutinate, it indicates that the blood does not have the antigens binding the special antibody in the reagent.
  3. 3. If you know which antigens are in the person's blood, it's easy to figure out which blood group he or she belongs to! whom?

Of course you can always give A blood to persons with blood group A, B blood to a person with blood group B and so on. But in some cases you can receive blood with another type of blood group, or donate blood to a person with another kind of blood group.

The transfusion will work if a person who is going to receive blood has a blood group that doesn't have any antibodies against the donor blood's antigens. But if a person who is going to receive blood has antibodies matching the donor blood's antigens, the red blood cells in the donated blood will clump.

Blood Group Antigens Antibodies Can give blood to Can receive blood from

AB A and B None AB AB, A, B, 0

A A B A and AB A and 0

B B A B and AB B and 0

0 None A and B AB, A, B, 0 0

Blood Group Antigens Antibodies Can give blood to Can receive blood from

AB A and B None AB AB, A, B, 0

A A B A and AB A and 0

B B A B and AB B and 0

O None A and B AB, A, B, 0 O

Other blood groups Why Blood Donation Is Imperative

Several other blood group antigens have been identified in humans. Some examples: MN, Bombay Duffy, Lewis, Kell.

They, too, may sometimes cause

  • Transfusion reactions and even
  • Hemolytic disease of the newborn

In cases where there is no ABO or Rh incompatibility. Bleed and be a donor

To save a life in danger

People who lose blood in accidents, premature babies, major surgeries, patients suffering from dengue, cancer etc. Need blood. A proper supply of blood is essential for a person's existence. In India, in every two seconds someone is in need of blood. In a year nearly 41 million units of 250 cc blood is needed in India and out of which only a meager quantity of half million is provided by the existing systems of blood donation. In other countries it is worse than in India. As blood can be not stored indefinitely someone has to volunteer to donate blood at the moment in which blood is needed. Delay will prove fatal to the person who is in need of blood urgently. So it is essential and vital that people must understand the importance of blood donation and volunteer themselves to donate blood. They must consider this as a sacred duty to their fellows and take it as a social obligation.

Who can be a donor

A donor must fulfil the following conditions.

  • a) He must be above 18 years of age
  • b) He must be healthy and weight at least 50 Kgs.
  • c) He must not be suffering from any disease (Cancer, AIDS, Contagious diseases etc) high Blood Pressure or any other disorder ….
  • d) He must not be a drug addict…..

What he must do and what he must not do

  • 1) A donor must avoid smoking on the day in which he donates his blood. Of course he can smoke three hours after the donation.
  • 2) He must not consume alcohol for 48 hours before the donation. (He must abstain from drinks for that day even after the donation.)
  • 3) He must take a good meal at least 3 hours before the donation.
  • 4) He must take snacks after the donation and take a good meal later.
  • 5) He must take fluids in plenty. The donor will not feel drained or tired if he takes fluids.
  • 6) He must refrain from heavy exercises for 12 hours after donation
Reality of Blood Donation

Types of Blood Donation.

Blood donations are divided into groups based on who will receive the collected blood. "Allogeneic" (homologous) donation happens when a donor gives blood for storage at a blood bank and transfusion takes palce to an unknown recipient.

A "directed" donation happens when a person donates blood for transfusion to a specific individual.

A "replacement donor" donation is found usually in developing countries. In this case, a friend or family member of the recipient donates blood to replace the stored blood that is used in a transfusion, ensuring a consistent supply.


Donors are required to give consent for the process and this requirement means minors cannot donate without permission from a parent or guardian. The donors race or ethnic background is sometimes considered for certain blood types, especially rare blood groups.