Stephanie Goodman, age 11, of East Brunswick, N.J., for her question:
WHAT MAKES DIFFERENCES IN BLOOD?
An average adult weighing about 160 pounds has about five quarts of blood running through his body. An 80 pound child has about half this amount while a newborn 9 pound baby will have about 10 ounces of blood. If you live in high altitudes, where there is less oxygen than closer to sea level, your body has a greater amount of blood than do flatlanders.
Blood flowing through your body is actually your life stream. The blood supplies your cells with food and oxygen which you need for growth and health. It also carries all waste products to special organs that remove them from your body. In addition, blood also fights disease germs that may enter your body.
Your blood has four main parts: plasma, red blood cells, white blood cells and platelets. The red and white cells are sometimes called corpuscles. All people have these same elements in their blood.
Scientists have discovered, however, that there are many different types of blood. Just as nature has chosen to give humans many variations in body structures, so has nature chosen to provide differences in blood types.
Blood types are determined by the presence or absence of certain antigens on the membrane of the red blood cells. An antigen is a molecule found on some blood cells and some respond to foreign matter by producing substances called antibodies. Antibodies are particles of a certain protein that destroy the intruders. It’s a complicated business.
In 1900 an Austrian American scientist named Karl Landsteiner determined the ABO blood types and found there were four based on the presence or absence of two antigens called A and B. The blood types were A, B, AB and O.
Forty years later Landsteiner and an American scientist named Alexander Wiener discovered another erythrocyte antigen, the Rh factor. Most people have the Rh factor on the surface of their red blood cells and their blood is called Rh positive. A few are without this antigen, and we class them as having Rh negative blood. The Rh factor plays an important part in blood transfusions. Doctors are. extremely careful when they determine a donor’s blood type for one of their patients.
When a pint of blood is put into a blood bank, it is tested and classified by ABO and Rh types before it is refrigerated and stored.
Blood transfusions are used to replace blood that might have been lost during surgery, and also goes to many who have had accidents or certain diseases. In addition, transfusions of blood are used to treat certain types of anemia, low platelet counts and shock.
The world’s first blood bank was established at Mayo Clinic in Rochester, Minn., in 1935. Now there’s one in almost every hospital.