(Editor’s note: This article has been corrected to urge people to contact Canadian Blood Services to learn about donating blood.)
Blood is a substance that many myths have grown up around.
Perhaps the most pernicious is that of being a “pure-blood.” This term means that the person possessing it has a genetic inheritance that is pure – whatever that means. It is usually used to denote some form of superiority of one person or organism over other more mongrel types. It has been used to justify slavery and mass murder in our long and “bloody” history.
The truth about blood is much more interesting, if less significant, in a social way. Blood is a fluid that circulates throughout the body carrying nutrients, oxygen and waste products for use or disposal. The average adult body contains about five litres of blood.
The old phrase, “blood is thicker than water,” is true, but only by a bit. Blood has a density just over that of liquid water and comprises plasma — the liquid component of blood, red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes). These components allow blood to perform its functions and plug up any leaks in the circulatory system.
The red blood cells are the workhorses. They are unlike most cells in the body. They do not have a nucleus and have sugar coatings on their surface that create the different blood types. They are primarily concerned with transport of oxygen from the lungs to the body. Hemoglobin, a complex molecule that uses iron as an oxygen transport medium, forms most of the red blood cell’s machinery.
The red blood cells pick up oxygen in the lungs and transport it to the rest of the body. The surface area of these cells is about 2,000 times greater than the surface area of your skin and it is this tremendous, reactive surface, that allows the blood to carry lots of life-giving oxygen. The result of the body’s use of oxygen is the production of carbon dioxide. Interestingly, this waste product is mostly carried by the plasma portion of the blood.
The white blood cells are one of the body’s main defense mechanisms. These large cells patrol the bloodstream and even prowl between the tissues to seek out and destroy invading bacteria that can cause infection. The numbers of white blood cells can vary from a normal of about 0.7 per cent of the blood to much greater during times of bacterial invasion.
The final constituent of blood are platelets. These cells are involved in body repair. Should an injury occur that ruptures the blood vessels, through a complex process, a chemical called fibrin creates a mesh over a platelet plug at the site of the injury. We call this process clotting and it keeps us from bleeding out when our skin is punctured.
Blood can be classified into several “types” based upon the sugar coatings on the surface of the cells. The basic blood types are A, B, AB, and O. A and B refer to these sugar coatings on the cells. Type A has one kind of sugar, type B another and type AB has both. Type O is unique in that it has no sugar coating. In giving blood from one person to another you must be careful to match blood types. Giving a person with type A blood a transfusion with type B blood or type AB blood can cause a severe immune response and kill the donated cells and possibly kill the patient.
The exception is type O blood. As this kind of blood has no sugar coating, it can be given to persons with type A, B, and AB blood types. These people are called universal donors. There are some complications with something called RH factors having to do with specific antigens in the blood, but the principle is the same. The ideal donor is a person with type O negative blood.
Recently, scientists at the University of British Columbia have found a way to convert type A, B and AB blood into type O. This discovery should ease the shortage of blood for transfusion and make this life-saving product more available for surgery, and accidents.
One of the best ways to save lives is to give blood. It is a mostly painless procedure that can be the gift of life for people in need. Contact Canadian Blood Services at 1-888-236-6283 or blood.ca to learn about blood donation clinics in your area.
Tim Philp has enjoyed science since he was old enough to read. Having worked in technical fields all his life, he shares his love of science with readers weekly. He can be reached by e-mail at: email@example.com or via snail mail c/o The Expositor.