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Blood accounts for about 8% of human body weight. A typical adult has about 80 mL of blood per kilogram of body weight, although this varies somewhat with age and gender. (Example: A person weighing 60 kg would have slightly less than five liters of blood in total.) Blood is 45% blood cells (red blood cells, white blood cells, platelets) and 55% plasma (the liquid component of blood).
Plasma is a straw-yellow colored solution of various substances in a concentration of about 10%. The main substances in plasma (besides water) are various proteins; the other substances in plasma include electrolytes, sugar and fats. “Serum” is plasma from which the clotting proteins (fibrinogen, etc.) have been removed.
Blood performs several functions that are essential to life. Normally, the various kinds of blood cells and constituents of plasma maintain an optimum functional balance. But if this balance is upset because of abnormalities of volume or quality in these constituents, then it can be a cause of serious illness. On the other hand, with a deeper understanding of the relationships between these blood constituents, we can take advantage of their respective functions to directly remove causes of disease or to rebalance the body’s internal environment so that treatment is effected.
A basic explanation of blood constituents and their functions, and how these relate to removal of harmful substances through therapeutic apheresis.