I am not sure where I ripped this off from, somewhere on the interwebs:
very handy Understanding your lab tests
A QUICK LESSON IN BLOOD COUNTS...
Red blood cells or erythrocytes comprise a third of all the cells in the human body. With about 20 trillion in the average adult, they're not only the most common cells in the human body, they are also the only cells that don't have a nuclei. The red blood cells' primary function is to carry oxygen to the body's tissues, and because they are 40 percent lighter than they would be with nuclei, it is easier for the heart to pump them through the circulatory system.
Red cells contain a molecule called hemoglobin, which picks up oxygen as the cells travel through the blood vessels in the lungs. After red cells leave the lungs they get distributed throughout the body, passing through ever-smaller vessels called arterioles and capillaries. There they get forced up against the vessel walls like passengers in a crowded subway train. Under that pressure, the oxygen molecules pop off the hemoglobin and get taken into the vessel walls and passed on to neighboring cells. Relieved of their burden, the red cells pick up carbon dioxide, which they then carry back through the veins to the lungs to be exchanged for new loads of oxygen.
White blood cells or leukocytes, are the
body's border defense: they are responsible for apprehending and eliminating
foreign substances. They're larger but much less numerous than red blood cells,
numbering about 20 million in the adult body. While red cells are buoyed along
like cargo rafts as the heart pumps the serum, white cells function more like
patrol boats. Under their own locomotion, they can change direction to go after
an invading molecule or cell.
There are three basic types of white cells-granulocytes, monocytes and lymphocytes-each with its own specialized tasks. Granulocytes, the first line of defense, home in on bacteria or any other foreign substance in the blood. They are filled with granules containing chemicals that destroy their prey. One type of granulocyte, the neutrophil, is an all-purpose search-and-destroy agent that makes up 60 percent of white blood cells. The other two granulocytes, eosinophils and basophils apprehend special intruders such as allergens and parasites and account for 3 percent of the white blood cell population.
About 33 percent of white cells are lymphocytes, the brains of the immune system. They send out antibodies to immobilize foreign molecules and chemical messengers that spur other cells into action. The remaining 4 percent of white blood cells are monocytes, which clean up cellular debris and devour invaders that have been tagged with antibodies. (Like what happens to the red blood cells, platelets and sometimes white blood cells themselves in Evans syndrome when they have been tagged with antibodies.)
There are three basic types of white cells-granulocytes, monocytes and lymphocytes-each with its own specialized tasks. Granulocytes, the first line of defense, home in on bacteria or any other foreign substance in the blood. They are filled with granules containing chemicals that destroy their prey. One type of granulocyte, the neutrophil, is an all-purpose search-and-destroy agent that makes up 60 percent of white blood cells. The other two granulocytes, eosinophils and basophils apprehend special intruders such as allergens and parasites and account for 3 percent of the white blood cell population.
About 33 percent of white cells are lymphocytes, the brains of the immune system. They send out antibodies to immobilize foreign molecules and chemical messengers that spur other cells into action. The remaining 4 percent of white blood cells are monocytes, which clean up cellular debris and devour invaders that have been tagged with antibodies. (Like what happens to the red blood cells, platelets and sometimes white blood cells themselves in Evans syndrome when they have been tagged with antibodies.)
Platelets, so named because they are
shaped like tiny plates, release chemicals that promote clotting when blood
vessels are broken. These chemicals work by assembling a blood protein called
fibrin into a meshwork over the damaged area. The mesh serves as a net to trap
blood cells and proteins, which eventually form a plug in the damaged vessel
wall.
The meaning of the numbers:
A complete blood count involves computing the number of red cells, the percentage of red cells in the whole blood, the size of the average red cell (an indication of its robustness), the average amount of hemoglobin per red cell, and how much there is in the blood. In addition, a physician will want to calculate the total number of white cells and the percentages of the different types of white blood cells, which can be distinguished under a microscope by the shapes of their nuclei. A physician will compare the numbers of cells in a sample of a patient's blood, with the average number of cells in the same amount of blood from a healthy person.
Having too few red blood cells or too little hemoglobin is called anemia.
Having too few white blood cells is a sign that a person's immune system is not functioning properly.
Too many white blood cells usually means that the patient has an infection.
The type of white cell that is over produced can indicate the extent of infection. An increase in the number of neutrophils, for example, means the person probably has a bacterial infection. An increase in lymphocytes and basophils usually corresponds to an allergic reaction like what you might get from ragweed. If there are far too many white blood cells-in the neighborhood of 100,000-the patient may have leukemia. A physician will also look at the number of platelets in the specimen to assess if the patient may have too few or too many.
A complete blood count involves computing the number of red cells, the percentage of red cells in the whole blood, the size of the average red cell (an indication of its robustness), the average amount of hemoglobin per red cell, and how much there is in the blood. In addition, a physician will want to calculate the total number of white cells and the percentages of the different types of white blood cells, which can be distinguished under a microscope by the shapes of their nuclei. A physician will compare the numbers of cells in a sample of a patient's blood, with the average number of cells in the same amount of blood from a healthy person.
Having too few red blood cells or too little hemoglobin is called anemia.
Having too few white blood cells is a sign that a person's immune system is not functioning properly.
Too many white blood cells usually means that the patient has an infection.
The type of white cell that is over produced can indicate the extent of infection. An increase in the number of neutrophils, for example, means the person probably has a bacterial infection. An increase in lymphocytes and basophils usually corresponds to an allergic reaction like what you might get from ragweed. If there are far too many white blood cells-in the neighborhood of 100,000-the patient may have leukemia. A physician will also look at the number of platelets in the specimen to assess if the patient may have too few or too many.
While normal values vary slightly from
institution to institution, the following values are within the accepted range
of normal:
- Red blood cells 4 -5.3 million/mm3
- Hemoglobin 11 - 14.5g/dl
- Hematocrit 34-42%
- White blood cells 3.6 - 11.1 K//mm3
- Platelets 165-353 K/mm3
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