Investigations in blood

William Harvey's monumental achievement in discovering the circulatory system inspired two of his friends to dabble in the study of blood — Christopher Wren, the architect who designed St. Paul's Cathedral and other remarkable London buildings (Wren was an astronomer before he turned to architecture), and Robert Boyle, a pioneer in modern chemistry.

The men were all members of the Experimental Philosophy Club in Oxford, England, and admirers of the work of Francis Bacon, who advocated first-hand investigations into the natural world, rather than accepting long-held orthodoxies.

At the time, it was thought that the blood was impervious to anything that came from the outside world. Using a prototypical syringe made of a quill and a bladder, Wren and Boyle injected dogs with opium and other drugs, and showed that the dogs were affected — that they reacted to the opium, for example, by falling asleep.

These experiments inflamed the scientific community, and no end of creatures were injected with every kind of fluid, from urine to milk, sometimes with fatal results.

Richard Lower, an Oxford-trained doctor and protege of Wren and Boyle's, in 1665 decided to see what happened when he injected a dog with blood from another dog, connecting the two vein-to-vein. The experiment failed. The blood just pooled up in the connecting tube, Douglas Starr relates in his book, Blood: An Epic History of Medicine and Commerce.

Then, Lower tried tapping an artery in the donor dog, and this time the experiment worked. The stronger pressure from the arterial blood made for a successful transfusion, leading Lower to reason that "one Animal may live with the blood of another," Starr writes. Lower's experiments set off a frenzy for transfusions in England and, soon, in France.

Jean-Baptiste Denis, one of the French King Louis XIV's doctors, thought he might cure violent people of their rages by transfusing them with the blood of gentle animals like calves and sheep. At the time, people believed that blood contained a sterotypical set of characteristics of the creature that possessed it. For a while, it looked like Denis had had a stroke of genius, as one violent character in particular seemed for awhile utterly transformed.

Lower was furious, accusing Denis of stealing his work. Meanwhile, some human transfusion subjects began to die (blood being much more complicated than these men understood), including some high-profile patients of Denis. The French Parliament banned transfusions in 1670, followed by the British Parliament and eventually the pope.

That was the end of transfusions in Europe until the early 19th century.

Still, Starr writes, these early researchers "cracked the wall of humoral medicine, showing that the body was ruled not by vague humors but by chemicals, vessels and pumps."

Our inner sea

Aeons ago, life on earth consisted of single cells suspended in the primordial sea. They took their nourishment directly from the surrounding waters, and excreted their waste products to be carried away, automatically, by the currents.

As more complicated animals evolved, the sea became private and internal in the form of blood, but it retained the original salts and the chemically useful pH, or acid-alkaline balance, of roughly neutral. When the first creatures slithered onto land, they took that inner sea with them.

The balances have changed slightly in the millions of years since then, but the individual cells of the human body are as dependent on the blood’s constancy as the first cells were on the never-changing sea.

From Shock-Trauma (1980), by Jon  Franklin and Alan Doelp

Red river

Blood is actually connective tissue, the only liquid type in the human body.

How much blood we have depends on how big we are — blood accounts for about 8 percent of body weight, on average about five quarts (roughly five liters). More than half of blood is plasma, a yellowish fluid that itself is mostly water.Blood splatter

Plasma carries all the things the cells need when it begins its journey out from the heart. The bulk of its cargo is the 25 trillion red blood cells filled with oxygen, but it also carries infection-fighting white blood cells and platelets that will clot the blood when needed, as well as vitamins, electrolytes, hormones and other materials.

Animals that use a protein called hemoglobin to store oxygen have bright red blood when it's fully oxygenated, because hemoglobin contains iron. (Spider blood, for example, contains copper-rich hemocyanin, and is blue when oxygenated.)

Red blood cells are manufactured in bone marrow, and circulate in the blood for about four months. They look like fat plates, flat but curved, a shape that allows them to squeeze into capillaries. They have no nucleus, devoting as much space as they can to hemoglobin.

One entire circulation of the blood through the body of the average resting adult, given that five quarts of blood, takes about one minute. Without the life-giving oxygen it carries, the most vulnerable cells, including those in the brain, would begin to die within about five minutes, and organs would start shutting down just a few minutes later.

Image from Wikimedia Commons

The heart of the matter

The circulatory system is all about distributing oxygen around the body. The mighty heart — which never rests as long as we live — the 60,000 miles worth of blood vessels, and blood itself, all come down to this: Every cell in our bodies needs a fresh supply of oxygen every few minutes, or it will die. And so will we.

Diagram of the human heart

The human heart

The heart is at the center of the circulatory system, a hollow organ composed of muscle and connective tissue. In humans, the heart has four chambers — two atria or "entrances," and two ventricles or "bellies" — and weighs less than a pound.

The heart beats optimally about 70 times a minute throughout our lives, beginning within three weeks after conception, for a total of about 3 billion pulses in a lifetime of  80 years.

The heart pumps blood to the lungs, where it picks up its cargo of oxygen, and then on to the rest of the body.  Valves in the heart and the blood vessels ensure that blood travels in one direction only, away from the heart in the arteries, and toward the heart in the veins.

Red blood cells travel single-file through the capillaries, the fine vessels that connect the arteries and the veins, to deliver oxygen and other nutrients to the cells. Here the blood takes on waste, especially carbon dioxide, which it will deposit in the lungs for expulsion into the air.

A septum in the middle of heart keeps waste-filled blood returning from its journey through the body separate from oxygenated blood fresh the lungs.

Here in the heart, over and over, the journey begins again.

Image from http://commons.wikimedia.org

Fascinated with blood

I'm embarking on a series of posts about blood. I can't help it. I'm fascinated with blood.

The final classic symptom of amniotic fluid embolism is disseminated intravascular coagulation (DIC). When I suffered an AFE during the birth of my younger daughter, I was nothing but classic.

Edward Cullen
Also fascinated by blood

I hemorrhaged to the point where all the blood ran out of my body three times over. I didn't die from this event because I received a total of 87 units of blood and blood products — whole blood, plasma, cryoprecipitate and extra clotting factor.

I am alive to tell our birth story because thoughtful strangers had donated their blood, a large stockpile of blood was five minutes away when I needed it, and because a whole raft of people had done the work over centuries to figure out how to make someone else's blood work in my body.

And, by 1997, the blood supply had been made safe again, after a horrific tainting with the HIV/AIDS virus.

The bill for my daughter's birth, including two surgeries (a Caesarean section and separate hysterectomy performed to stop the bleeding), a stint for the baby in the high-risk nursery, a night for me in the intensive-care unit and an additional four days in the hospital, was $100,000 all those years ago.

Blood accounted for $13,000, more than 10 percent of the total.

Blood was a major factor in giving our birth story a happy ending. Fascinating!