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Blood Typing



By simply looking at a sample of human blood, it wouldn't seem like anything more than a red liquid. The truth is that blood is a complex fluid made up of many different components, each with a specific job. The first analysis of blood was carried out by Marcello Malpighi in 1661, who discovered that much of blood is composed of large red cells that have no nucleus. These cells are called erythrocytes, and we now know that they are responsible for gas exchange within the tissues of our body. Almost 200 years later, Joseph Davaire discovered that blood also has large white cells that move about like amoebas. Outnumbered by red cells by a ratio of 650:1, these white cells-leukocytes-help protect our bodies from foreign agents, such as bacteria and viruses. In addition to red and white cells, most human blood contains platelets and proteins that help clot the blood. All three of these components can be separated from the blood after donation and used for different purposes. The first successful human blood transfusion was accomplished in 1818 by James Blundell. In 1900, Karl Lanstreimer observed that the blood of one individual, when mixed with the blood of another, might cause hemolysis, the visible clumping of red cells. This observation resulted in the establishment of blood typing: the distinction of four blood groups-A, B, AB, and O. These different blood types are caused by the presence of a chemical marker-an antigen -on the surface of the type-A and type-B red blood cells. When mixed with the wrong blood type, these antigens are picked up by antibodies that cause the cells to clump. Someone with type-AB blood can receive any type blood with no ill effects, while people with type-O blood can only take their own type. People with type-A blood can receive A or O, and people with type-B blood can take B or O. This makes type-O blood the universal donor. Blood donors and recipients must be typed and matched very carefully before transfusions are given.


Find out how your blood type fits in with that of the general population. By classifying blood types, you can find out what type of blood is most common among your students, and whether this information is similar to national statistics. Materials
  • removable sticky notes
  • graph paper
  • pencils
  1. Have each student find out his or her blood type by asking at home, consulting a birth certificate, or reviewing a recent blood test.
  2. Pass around the note paper and have each person record his or her blood type on a separate sheet. Collect the notes and post them on a wall, sorting them by groups to form a simple bar graph.
  3. Record the number of individuals in each group.
  4. Based on the class population and the information in the segment, calculate how many potential donors are present for each blood group. (For example, those with type-A blood can receive blood from either type-As or type-Os.)


    Asimov, I. (1986) How did we find out about blood? New York: Walker & Co.
    Merz, B. (1992) Blood count: What is your doctor looking for? Good Housekeeping
    (Mar): 136-140.
    Villee, C., et al. (1989) Biology. Philadelphia: Saunders College Publishing.
    Additional source of information:
    American Red Cross
    National Headquarters
    17th and D Street NW
    Washington, DC 20006
    Community resources:
    American Red Cross chapter
    Blood banks