Ques. 1        What is Haemocytometer?

Ans.             It is an instrument used in counting blood cells.

Ques. 2        What is the purpose of this Instrument?

Ans.             Purpose of the Instrument : It is used for the total count of W.B.C., R.B.C., and Platelets.

Ques. 3        What is total count?

Ans.             It is total number of cells per cubic milimetre of blood. Parts of Haemocytometer : (1) W.B.C. pipette. (2) R.B.C. pipette. (3) Counting chamber (with cover slip). In addition to this, diluting solution is also required.

Counting Chamber : It is double counting chamber with 3 plat forms separated by wide grooves. The whole square of counting chamber is divided into 5 big squares.

In centre, for counting erythrocytes, each big square is divided into 25 small squares & each small square is sub-divided into 16 very small squares.. 4 big squares for leucocyte count are placed at 4 corners of the erythrocyte counting chamber & each big square is sub-divided into 16 small squares.

Ques. 4        Write short note on Blood Grouping.

Ans.             Blood Grouping : The blood group of an individual is inherited. The donor is so chosen that his corpuscles are not agglutinated by recipient’s serum. Before giving blood transfusion recipient’s blood should always be grouped and cross-matched.

Human blood contains agglutinogen (antigen) in the red corpuscles and specific agglutinin (antibody) in serum. The corpuscles may contain both ‘A’ and ‘B’ agglutinogen or only ‘A’ or only ‘B’ or no agglutinogen at all. If the corpuscles contain ‘A’ agglutinogen serum will not contain anti- ‘A’ agglutinin to prevent auto-agglutinogen the serum will not contain anti- ‘A’ agglutinin to prevent auto-agglutination. Human blood is grouped by Landsteiner in 1900 into AB, A, B and O groups. This grouping is based on antigen present in red cells and antibody present in one individual known as A.B.O. system.

  1. Group – AB : Its corpuscles contain A and B agglutinogen with no agglutinin in the serum. He can receive blood of any group, but can donate to A group only. He is called universal recipient.
  2. Group – A : This group contains ‘A’ agglutinogen and anti-B agglutinin. Its corpuscles will agglutinate the serum of group ‘O’ and ‘B’ His serum will not agglutinate corpuscles of group ‘A’ and ‘O’. Therefore, he can donate blood to group ‘A’ and ‘B’ and can receive blood from group ‘A’ and ‘O’ only.
  • Group – B : This group contains ‘B’ agglutinogen and anti-A agglutinin group. His corpuscles will be agglutinated by serum of ‘A’ and ‘O’. His serum will agglutinate corpuscles of group ‘A’ and ‘A’. Therefore, he can donate to group ‘B’ and ‘A’. He can receive blood from group ‘B’ and ‘O’.
  1. Group- O : This group contains no specific agglutinogen (antigen). Its corpuscles will not be agglutinated by any group, but his serum will agglutinate the corpuscles of all other blood group. Hence he is called universal donor.
  2. Rh System : Apart from A.B.O. antigens, human R.B.C. contains various other antigens without natural antibodies, of which Rh factor (Rhesus monkey factor) or antigen ‘D’ is the most important. The clinical importance of Rh system depends primarily on ability of antigen – D to induce antibody formation, when introduced into circulation of Rh negative patient. Rh – negative subjects may be sensitized with Rh positive blood. About 85% of human blood are Rh positive. When Rh-negative blood comes in contact with the Rh positive blood, there may be violent adverse reactions.

Ques. 5        How can we determine blood group?

Ans.             Determination of Blood Group :

Few drops of recipient blood are placed in 2 slides containing stock serum of anti-A & anti-B. The slides are rocked for couple of minutes, the results of agglutination are noted –

Patient’s corpuscles (agglutinogen) reaction

Signifies the patient group

(i) Anti-A Serum (Agglutinin)

(ii) No Agglutination

(iii) Agglutinated

(iv) Nil

(v) Agglutinated

Anti-B serum (Agglutinin)

No Agglutination




Group ‘O’

Group ‘A’

Group ‘B’

Group ‘AB’



If patient’s R.B.C. are agglutinated in both slides, the patient belongs to AB group. If stock serum anti-A is agglutinated, he is Group A. If the stock serum of anti-B is agglutinated, he is Group B. If no agglutination in either side, he is Group ‘O’

Rh Factor is determined with Special Tube Technique (or Coomb’s Test).

Cross Matching : The donor’s red cells are directly tested against recipient’s red cells against donor’s serum, no agglutination in either, donor’s blood can be safely transfused.

Complication of Blood Transfusion: (i) Pyrexial reaction. (ii) Allergic and sensitization reactions. (iii) Reactions due to over-transfusion. (iv) Reactions due to transmission of diseases, viz. Hepatitis, AIDS, Malaria, Syphilis, Bacteria etc. (v) Haemolytic reactions.

Ques. 6        How to send the patient’s Blood to the Blood bank for Grouping and Cross Matching?

Ans.             About 2 ml. of recipient’s blood is drawn with a syringe, to 10 drops of blood is added to vial containing 2 ml. of 3.8% sodi-citrate solution and the remaining whole blood is put into another vial to clot. These samples are sent to the blood bank after proper labeling. A note is sent if patient had received I.V. dextran immediately before.

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