MEDICALEXAMINER

Blood Inside The Body Is Blue

The titles of “Medical Mythology” installments usually describe the myth we’re about to discuss. Not so this time. Blood inside the body actually is blue, although with one important stipulation: for that to be true it has to be the body of a horseshoe crab, an octopus, a squid, or some other crustacean.

But otherwise it’s a no-go on the blue blood — most of the time

For example, skinks have green blood.

Also, as you may have noticed, humans and most other animals have red blood.

We all know this, but the rumor persists that human blood isn’t always red. When it’s hermetically sealed inside the body where it belongs, the tale sometimes told is that our blood is actually blue. “You can see that’s it’s blue, plain as day. Just look at the veins close to the skin’s surface. They’re blue.”

The reason we never see literal blue blood, as the story goes, is because the very instant blood is exposed to air it turns its familiar red color.

To set the record straight, human blood is always red, inside the body or out. There are different shade of red, however. All the time. In a single circuit through the body, the same measure of blood can go from bright red to maroon and back again. It not only can; it does. Put it this way: it better. And it does so three times a minute on average.

The reason for the color change is that freshly oxygenated blood, having just left the lungs for the heart to be pumped out to every corner of the body, is bright red. That is how the iron in hemoglobin reacts with oxygen: it turns bright red.

As blood makes its way through arteries, it delivers its precious payload, gradually depleting the oxygen it carries. It then circles back to the heart and lungs (not in that order) through veins for a fresh supply. That blood, the de-oxygenated variety, is no longer bright red, but it’s still definitely red, even if dark red, muddy red, or brick red.

True, there is no denying that veins just beneath the skin look at least bluish, if not downright blue.

The explanation: color is a funny thing. As we all learned in school, an object looks a certain color to us because it reflects back only that color from the visible spectrum of light. Oranges are perceived as orange because they absorb all wavelengths of the entire rainbow of color except orange; that narrow band of color is the only one that bounces off oranges and into our waiting corneas.

Scientists call our blue veins (the ones that aren’t really blue) an optical illusion created by how light is alternately absorbed or reflected by our skin and the underlying vein.

It should be noted in closing that many textbooks, encyclopedias and schoolbooks have diagrams showing red blood leaving the heart and blue blood returning there. Those colors are used simply to illustrate the way blood circulates, not as literal depictions of the color of blood within the human body.

The word “medical” is in quotes because it’s not exactly the appropriate word to describe the healthcare providers of the day.

They were in many cases the most well educated people in a town, city or village, but that education was rarely in medical arts. The village “doctor” was quite often the village priest, and medicine was often administered with a healthy dose of superstition, ignorance, and church dogma.

As the middle ages went on, barbers often doubled as healthcare providers. They were skilled with sharp blades, after all, and that was all that was needed for one of the most popular treatments of the day: bloodletting.

Unlike cars that might be a quart low, the belief persisted for centuries that humans could be a quart over in the blood department. That harkened back to Hippocrates and his teaching that four basic substances or “humors” (one of them being blood) controlled health. They all needed to be in perfect balance for good health and if they weren’t, let’s draw down a few pints. It always seemed to be only blood that was drained, however, probably because it wasn’t easy to drain black bile.

Another scary practice of the day was trepanation, shown below, named after the type of hole saw used to perforate the skull in order to — what else?

— cure epilepsy, headaches, and mental disorders, as well as release evil spirits. All without anesthesia.

In addition, all antibiotics and disinfectants — and even the barest acknowledgment of any need for them —were centuries away. The same was true of pain relievers, although various herbal and alcohol-based concoctions were offered. That was good because there were many treatments that offered no guarantee other than a level of pain far off any chart we could imagine today.

But it wasn’t all bad.

The 1600s saw a first-ever awakening of scientific fact over religious superstition. In fact, the Age of Enlightenment began during the 1600s, paving the way for such men as Galileo, Isaac Newton, John Locke, René Descartes, and Voltaire to think and act outside a box the church had drawn within very narrow confines and had vigorously protected for centuries. A discovery as basic as the earth circling the sun - the opposite of what the church taughtcould lead to public execution for its proponent.

William Harvey (1578-1657), the discoverer of the circulatory system, had to fight for acceptance of his work against the Catholic Church, which taught that the liver was the seat of life within the body.

Hopefully, people in distant centuries will shake their heads at what passes for the pinnacle of knowledge we claim to stand upon today. In the meantime, reflecting on what people had to endure 400 years ago might help us appreciate the progress we enjoy. We might not even mind sitting in a waiting room for two hours before an appointment.