Blood Read Free Page A

250 million red blood cells, 16 million platelets, and 375,000 white blood cells. If you can imagine blood in a test tube, separated by means of a centrifuge into its key parts, you will notice three distinct substances, each with its own colour and function. Let me quickly mention them, from top to bottom in their separated forms in our imaginary test tube.
    Plasma comes on top, as it is lighter than the other key blood ingredients. Made up of about 92 percent water (water accounts for about 50 percent of our blood), it is a yellowish, straw-coloured alkaline fluid. In it, you find many dissolved solids such as glucose (or sugar); proteins such as albumin, which controls the flow of water in and out of the bloodstream; hormones such as erythropoietin; and insulin, salts, lipids, and waste products such as bicarbonate ions, amino acids, and blood cells. I liken plasma to a river, offering a delivery system for the ingredients in blood, as well as carrying products that help regulate bleeding and clotting.
    It is possible to donate and receive plasma separately from other blood products. When blood is withdrawn from the body, the red blood cells, white blood cells, and platelets are separated and returned to the body of the donor, minus the plasma. Some of its key medical uses are to help people cope with bleeding or clotting disorders, recover from burns, deal with immune deficiencies, and survive complications resulting from bone marrow or organ transplants. Plasma can be stored for longer than regular blood products, and it can be frozen or dried for easy transportation. One additional advantage to plasma is that the donor’s body can replace plasma much faster than whole blood.
    In the tube of blood whose parts have been spun and separated in a centrifuge, the middle of the three layers contains the white blood cells and platelets. White blood cells are pale in colour. They are also known as leukocytes or white corpuscles. They come in different varieties. The primary roles of the white blood cells are to remove waste from the blood and to fight against infection. The language used to describe white blood cells is strangely military. They are said to surround and devour bacteria. They engulf, digest, and destroy invading micro-organisms. One type of white blood cells — accounting for about one-third of a healthy person’s white blood cell count — is known as lymphocytes. These include helper cells, suppressor cells, and natural killer cells. The killer cells are labelled “natural” after their function, which is not to attack invading organisms but to destroy the body’s own cells that are cancerous or carrying viruses.
    The white blood cells are commonly likened in our language to soldiers going to war on behalf of the nations that are our bodies, identifying, targeting, and destroying foreign invaders. The war and battle metaphors we employ — influenced by the writings of Louis Pasteur in the 1800s and reinforced by U.S. president Richard Nixon, who in 1971 signed the National Cancer Act and declared a “war on cancer” — offer one way to contemplate human biology. They certainly provide us with a method to imagine the body’s efforts to deal with disease and infection. At the same time, they are at risk of leaving us with the impression that people who succumb to illness simply did not try hard enough, and that people who overcome the same illnesses are stronger, more courageous, or have more valour. It is a striking way to refer to our own bodily processes, but there you have it.
    Platelets are, with white blood cells, part of the thin middle layer separating the plasma from the red blood cells. Platelets are fragments of blood cells called megakaryocytes, which reside in the bone marrow. (All blood cell lines, including platelets and red and white cells, originate in the bone marrow.) Platelets live for a short time — only a week or so. The human body produces