What Do You Know About Red Blood Cells?

Blood has probably always been associated with life. It is absolutely essential to the most basic functions of our body, fueling the cells that complete all of our bodily functions. While, it's often portrayed as a thick, red liquid, in fact, blood is extremely mobile and complex. And, while I've always known vaguely what blood does, I wanted to explore its properties more closely here, especially because so many of our health conversations involve mentions of blood. Blood, which makes up 7% of our body weight, is comprised of a 4 basic parts: plasma, platelets, white and red blood cells. Plasma, which is nearly 90% water, makes up a little more than half of blood. And while each part serves a unique role, I wanted to focus on the red blood cells which are probably the most important component of blood.

Red blood cells (RBC), or Erythrocytes, make up 45% of blood. RBC are predominantly made of hemoglobin, a complex substance that helps red blood cells carry oxygen from our lung, out to our whole bodies. The hemoglobin molecule contains certain heme groups with 4 iron atoms that link to oxygen molecules in the lungs. As the RBC travel throughout out blood vessels and capillaries, oxygen in released and spread to the rest of the body through the RBC membranes. Hemoglobin also carries the carbon dioxide waste back from tissues to the lungs for exhaling. In addition to their primary role as oxygen carriers, RBC also work in the immune system because, when a RBC breaks because of bacteria, the hemoglobin spills out and releases free radicals that break down the bacteria's cell walls and membranes, killing it. Without RBC, the hemoglobin would be free roaming in the plasma—which would make the blood too heavy to carry oxygen throughout our bodies. In fact, the RBC ability to contain, transport, and release oxygen is so important, it's what helped us evolve as vertebrates. This is because RBC allows for thinner blood, more oxygen intake, and overall better movement of oxygen to tissues.

Humans have about 2-3x10^13 RBC at a time (4-6 million RBC per microliter of blood). Men have about more RBC than women and those living in higher altitudes or have low oxygen tension also have more RBC. RBC's hemoglobin transports 98% of oxygen while the other 2% is dissolved in the plasma. The RBC in an average adult male stores about 2.5 grams of iron, which is good for carrying carbon dioxide and oxygen. The iron in RBC makes up 65% of our bodies' total iron amount. This is, of course, what gives blood an iron taste.

RBC, themselves, are produced through a process called erythopoeisis in red bone marrow. In large bones RBC are produced at the rate of 2 million per second. In embryos, RBC are produced in the liver. RBC develop from stem cells into mature RBC in about 7 days and live about 100-120 days. In 2008, scientists created an artificial RBC out of stem cells in a lab. They are working to find a way to create blood this way for transfusions. This discovery, of course, would be a huge breakthrough in the medical community.

When some RBC don’t have enough iron atoms, they have a hard time carrying enough oxygen to your body, leaving you tired and run-down. This is the basis of Anemia, which is also an indicator of more serious illnesses. A similar tiredness happens after a person donates blood because of the loss of oxygen-rich red blood cells and blood sugar. But your body regenerates blood quickly, though, which is why blood donation is ok. Learn more about giving blood at the American Red Cross site.

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