The Function of Blood

If we take a sample of blood then the sample is treated with an agent to prevent from clotting, and then spin that sample using a centrifuge, the blood sample will separate into two parts:

• The red cell will settle in the bottom
• The white cells settle on top of them forming the “buffy coat”.

Those fraction of red blood cells is called as hematocrit, generally it approximate of 45%, if the value is much lower than this, you must be careful because this is once of a sign having Anemia.

As a general, blood has two major functions:
1. Transport through the body of:

• Oxygen and carbon dioxide
• Food molecule (glucose, lipids, amino acids)
• Ions (e.g. Na+, Ca2+, HCO3-)
• Waste (e.g. urea)
• Hormones
• Heat

2. Defense of the body against infection and other foreign materials, all the WBCs participate in this defense.

Blood produce with two different kinds, first produce in the bone marrow, second are from a single type of cell called a hematopoietic stem cell. Actually blood producing by stem cell is very rare only about one of 10,000 bone marrow cell.

Producing blood cell by stem cell also can attached (probably by adherents junctions) to osteoblasts lining the inner surface of bone cavities, and also express a cell-surface protein designed CD34. Stem cell can produce by mitosis, two kind of progeny.