Are you wondering what blood is made of? Here’s an answer from ever reliable The Merck Manual of Medical Information: “Blood is a complex mixture of plasma [the liquid component], white blood cells, red blood cells and platelets.”

Plasma constitutes more than half of the blood’s volume and consists mostly of water containing dissolved salts (called electrolytes) and proteins. Albumin is the major protein of plasma. “Albumin helps keep fluid from leaking out of blood vessels and into tissues, and albumin binds and carries substances such as hormones and certain drugs,” the Merck manual says.

Red blood cells (also called erythrocytes) make up about 40 percent of the blood’s volume; they contain hemoglobin, a protein that gives blood its red color. White blood cells (leukocytes) are fewer in number than red blood cells, with a ratio of about one white blood cell to every 660 red blood cells.

Platelets (also known as thrombocytes) are cell-like particles smaller than red or white blood cells. They are fewer in number than red blood cells, with a ratio of about one platelet to every 20 red blood cells.

The adult human has about five to six quarts of blood (more than a gallon). “Once blood is pumped out of the heart, it takes 20 to 30 seconds to make a complete trip through the circulation and return to the heart,” the Merck manual says.

If you care to know, red blood cells, most white blood cells and platelets are produced in the bone marrow—that soft fatty tissue inside bone cavities. “Two types of white blood cells are also produced in the lymph nodes and spleen,” the Merck manual says.

Here’s what happens: “Within the bone marrow, all blood cells originate from a single type of unspecialized cell called a stem cell. When a stem cell divides, it first becomes an immature red blood cells, white blood cell, or platelet-producing cell. The immature cell then divides, matures further and ultimately becomes a mature red blood cell, white blood cells, or platelet.”

Blood plays a part in every major bodily activity. The New American Desk Encyclopedia states: “As the body’s main transport medium, blood carries a variety of materials: oxygen and nutrients (such as glucose) to the tissues for growth and repair; carbon dioxide and wastes from the tissues for excretion; hormones to various tissues and organs for chemical signaling; digested food from the gut to the liver; immune bodies for prevention of infection and clotting factors to help stop bleeding to all parts of the body.”

Blood also plays a major role in hemeostatis, as it contains buffer, which keep the acidity of the body fluids constant and, by carrying heat from one part of the body to another, it tends to equalize body temperature.

Recently, the World Health Organization (WHO) in the Western Pacific urged more people to donate blood voluntarily and regularly. “Many people owe their lives to selfless blood donors,” WHO Regional Director for the Western Pacific, Dr. Shin Young-soo said.

Blood transfusion is a unique technology that blends science with altruism. Though its collection, processing and use are technical, the availability of blood depends entirely on the generosity of the donor who gives a gift of life.

Samuel Pepys recorded the first blood transfusion in his celebrated diary. On November 14, 1666, Pepys wrote that Richard Lower of the Royal Society made the first direct blood transfusion from the artery of one dog to the vein of another. Mr. Lower used quills to convey the blood.

In 1818 Dr. James Blundell, a British obstetrician, performed the first successful transfusion of human blood, for the treatment of postpartum hemorrhage. He used the patient’s husband as a donor, and extracted four ounces of blood from his arm to transfuse into his wife.

Twenty-two years later, at St. George’s Hospital Medical School in London, Samuel Armstrong Lane, aided by Blundell, performed the first successful whole blood transfusion to treat hemophilia.

According to the United Nations health agency, a single unit of donated blood can save up to three lives. “Blood transfusions can help patients suffering from life-threatening conditions live longer with better quality of life,” the WHO said. “Blood and blood products also have an essential, life-saving role in the care of mothers and young children.”

Globally, an estimated 289,000 women died in 2013 due to complications in pregnancy and childbirth. Of those deaths, 27 percent were due to severe bleeding.

The safest blood donors are voluntary, nonremunerated blood donors from low-risk populations, because they are motivated by altruism, a sense of moral duty or by social responsibility. The only rewards they receive are personal satisfaction, self-esteem and pride.

So you want to donate blood? The Merck manual gives this information: “The donor sits in a reclining chair or lies on a cot. A health-care worker examines the inside surface of the person’s elbow and determines which vein to use. After the area immediately surrounding the vein is cleaned, a needle is inserted into the vein and temporarily secured with a sterile covering. A stinging sensation is usually felt when the needle is first inserted, but otherwise the procedure is painless. Blood moves through the needle and into a collecting bag. The actual collection of blood takes only about 10 minutes.”

Generally, donors are not allowed to give blood more than once every 56 days, according to the Merck manual.

“Despite the advancements in science, artificially synthesizing blood remains impossible,” Shin said. “We are grateful for all those who make blood donation a regular part of their lives, and we urge many others to do the same. Together, we can save many lives.”


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