The old maxim says “write what you know,” and after four years of college and seven years working in a hospital laboratory, I know blood.
Did you know that blood can be used as more than a gratuitous special effect in Tarantino movies or nourishment for vampires? It’s true!
For much of man’s existence, little was known about the vital life force that flowed within each of us. It was only in 1628 that William Harvey proved that blood actively circulates through our vasculature rather than passively sloshing around. Almost 50 years later, in 1674, the man credited with inventing the microscope, Antony van Leeuwenhoek, noted that blood contained cells.
For tens of thousands of years, blood was magic to us. It was used in rituals and rites. Men spoke of bloodlines and blood sacrifices. An awe of blood has been so deeply ingrained in our psyches that it’s fairly common for people to feel dizzy or to faint just from seeing it.
My education and experience with blood has dispelled a lot of the mystery, but has done nothing to dampen the awe. Blood is beautifully complex, and my appreciation for it has only grown the more I learn.
If anyone is under the impression that blood is just simple delivery system for oxygen and carbon dioxide, they’re wrong. If it were that simple, science would be able to produce an artificial homologue, a synthetic blood that could serve that purpose. They can’t, and it’s not for lack of trying. If any attempt to make synthetic blood in the last 100 years had been successful, you wouldn’t be getting calls from blood centers asking you to donate.
So what is blood?
If you drew your blood into a tube and spun it at 4000 rpm for about five minutes, you’d find that it separates into three layers.
The top 50-55% is a pale yellow liquid component, called serum if the blood inside has clotted or plasma if the tube contains an anticoagulant. Plasma is not just a liquid that carries cells around. It contains hundreds of vital compounds: electrolytes, enzymes, proteins, lipids, hormones, clotting factors, antibodies, cardiac markers, tumor markers, viral or bacterial particles, therapeutic drugs or drugs of abuse — almost all the blood testing that is done in the lab is performed on the plasma component.
The next layer, commonly called the “buffy coat,” is generally a thin, milky film that contains white blood cells and platelets. White cells, or leukocytes, come in a variety of types, including neutrophils, monocytes, T and B lymphocytes, eosinophils, basophils, and NK (natural killer) cells, each with their own specific role to play in immune responses to pathogens, tumor cells, and allergens. Leukocytes are also the source of DNA used genetic testing. Platelets are involved in clotting, and are actually tiny bits of cytoplasm that have broken off from large cells called megakaryocytes in your bone marrow. In cases of acute leukemia or lymphoma, where white cells proliferate out of control, the buffy coat can be much thicker. In late stage sepsis or chemo treatment, where many white cells have been obliterated, there may be no buffy coat at all.
The bottom layer, about 45-50% of the total volume in healthy people, is the red blood cells. That percentage of red cells in whole blood is called the hematocrit, and when it falls below 35%, you are considered anemic. Red blood cells get their color from hemoglobin, a complex protein that not only holds an iron ion that binds oxygen, but also buffers the pH of your blood within the slightly alkaline range your body requires. A number of genetic defects affect the composition and function of the hemoglobin protein. The most well-known are sickle-cell anemias and thalassemias. A number of nutritional, genetic, cancerous, and infectious states can affect the size, shape, number, and appearance of red cells, white cells, and platelets, and laboratory personnel performing microscopic scans are often key to providing clues for a timely diagnosis.
Blood is vital. Blood is a wealth of information. Blood is beautiful.
Do you find all of this as fascinating as I do? You might consider a career in laboratory science. Click here for more info, or contact me on Twitter @SirEviscerate