Student’s question 4 : “By looking at a blood sample, how do you know what type of blood group it belongs in?”

This post is a response to a question by and A& P student on the post of “Why is blood red?”

Blood Typing can be very confusing, but it does not have to be. The more you look at it and try to go over it, either with a friend/classmate, or just reading this blog post, it gets easier…we promise.

There are different blood groups, 4 types. O blood group, A blood group, B blood group, AB blood group. We also have the rhesus factor Rh.

How did they arrive at this?

Our red blood cells carry what is called ‘antigens’ which are basically markers or labels. If Mr John’s red blood cells carry antigen A, then his blood group is A and if Ms. Jane’s red blood cells carry antigen B, her blood group is B. If Mr Bob has both A and B antigens on his red blood cells, then his blood group is AB. If Ms Karen has no antigen on her red blood cell, then her blood group is O.

But that’s not all…

In addition to the antigens that they carry on their red cells, they also carry antibodies(chemicals to fight against other antigens) in their plasma.

So Mr John whose blood group is A ( because he has the A antigen) would carry anti- B antibody in his plasma
Ms Jane whose blood group is B ( because she has the B antigen) would carry anti-A antibody in her plasma
Mr Bob whose is blood group AB ( because he has both A and B antigens) has NO antibodies in his plasma
Ms Karen whose blood group is O ( because she has no antigens) has both anti-A and anti-B antibodies in her plasma


Does that make sense?

It therefore means that anytime antigen A comes in contact with anti- A antibody, there is bound to be a fight! We see the reaction as clumping of the mixture – The proper term for clumping is AGGLUTINATION.

Blood typing uses this agglutination principle to determine what type of antigen a person is carrying on his/her red blood cells. This is then used to determine the person’s blood group. Here is what the test looks like:

Remember: Whenever there is clumping, it means there is an antigen and an antibody in contact! If we know what the antibody is, then we can safely guess what the antigen is.

Since Ms Karen whose blood group is O has no antigens, she can give blood to anyone ( Universal donor) but can only receive blood from another person with blood group O.

On the other hand, since Mr Bob whose blood group is AB, has no antibodies in his plasma, he can receive blood from everyone ( universal acceptor) but can only give to AB blood group.

Do you have any questions about blood A& P? Post it in the comment section below and we will get back to you ASAP!!



4 Comments Add yours

  1. Anonymous says:

    Hey can you do cardiac muscle contraction please?

    Liked by 1 person

    1. Sure, will let you know when we have posted a response to your question!


    2. Hi!
      We have posted an answer to your question. If you have anymore questions, just post it and we will answer ASAP!!!

      Find your response at this link:


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