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Blood Transfusions
| Article
# : |
10925 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
7 / 1986 |
2,944 Words |
| Author
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Marlene Z. Bloom
Marlene Bloom is a health and medical writer who resides in
Arlington, Virginia. |
In an age in which spectacular medical advances have become frequent occurrences, the drama that led to the development of blood transfusions seems to be overshadowed by more recent achievements. Yet blood--an essential human tissue--is donated to and received by thousands of people each day.
Although blood transfusion is taken for granted today, countless medical and surgical procedures could not take place without it. Each year more than 12 million units of whole blood are collected, and about four million patients--accident victims, those undergoing surgery, and patients with cancer and other diseases--receive blood, according to the American Association of Blood Banks (AABB).
The transfusion of blood has become one of medicine's most important and most widely used procedures, saving thousands of lives. Blood is a living tissue composed of cells suspended in a watery fluid called plasma. The cells--red blood cells, white blood cells, and platelets--make up about 45 percent of the blood by volume. Plasma makes up the remaining 55 percent.
The main functions of the red blood cells are to carry oxygen from the lungs to the body's cells and to bring the waste product, carbon dioxide, back to the lungs where it is exhaled. White blood cells protect the body against infection and disease; some fight invading bacteria by surrounding and destroying them while others play an important role in developing the body's immunity to disease. Platelets help blood clot when a person bleeds.
The average adult has approximately one billion red cells in each two or three drops of blood, or 30 trillion red blood cells in the blood stream. There is one white cell for every 600 red cells, and one platelet for every 10 or 20 red cells.
Plasma transports the water and nutrients obtained from food to all the cells of the body, as well as minerals and hormones essential to normal body function. It carries various waste products to the kidneys for excretion. Plasma also contains a number of proteins and other substances vital in maintaining health.
About 7 percent of a person's weight is blood, and the volume of blood varies according to height and weight: an average-size man has about 12 pints of blood and an average-size woman has about nine pints of blood.
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