Red Blood Cells
Red blood cells perform the most important blood duty. A single drop of blood contains millions of red blood cells which are constantly traveling through your body delivering oxygen and removing waste. If they weren't, your body would slowly die.
Red blood cells are red only because they contain a protein chemical called hemoglobin which is bright red in color. Hemoglobin contains the element Iron, making it an excellent vehicle for transporting oxygen and carbon dioxide. As blood passes through the lungs, oxygen molecules attach to the hemoglobin. As the blood passes through the body's tissue, the hemoglobin releases the oxygen to the cells. The empty hemoglobin molecules then bond with the tissue's carbon dioxide or other waste gases, transporting it away.
Over time, the red blood cells get worn out and eventually die. The average life cycle of a red blood cell is 120 days. Your bones are continually producing new blood cells, replenishing your supply. The blood itself, however, is re-circulated throughout your body, not being remade all of the time.
Since the human body is continually making more blood, it is safe for healthy adults to donate blood. The blood is then stored for use in emergency situations. Initially after giving blood, the donor may feel some momentary lightheadedness due to the loss of oxygen-rich red blood cells and blood sugar. The body quickly stabilizes itself.
White Blood Cells
Whenever a germ or infection enters the body, the white blood cells snap to attention and race toward the scene of the crime. The white blood cells are continually on the lookout for signs of disease. When a germ does appear, the white blood cells have a variety of ways by which they can attack. Some will produce protective antibodies that will overpower the germ. Others will surround and devour the bacteria.
The white blood cells have a rather short life cycle, living from a few days to a few weeks. A drop of blood can contain anywhere from 7 000 to 25 000 white blood cells at a time. If an invading infection fights back and persists, that number will significantly increase.
A consistently high number of white blood cells is a symptom of Leukemia, a cancer of the blood. A Leukemia patient may have as many as 50 000 white blood cells in a single drop of blood.
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