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Blood Test 101: Understanding Red Blood Cell Development
Dec 2, 2022 Susan Yox, RN, EdDFreelance Writer and Editor
Red blood cells
For people living with cancer, blood tests are performed often. Have you ever wondered what these tests mean? Let’s start with examining the life of a red blood cell (RBC). RBCs are a type of cell that contains hemoglobin, a protein that carries oxygen from the lungs throughout the body, and are produced in the bone marrow.
Every cell with a nucleus has the potential to divide and make new cells. However, red blood cells (RBCs) have no nuclei. These cells lose their nuclei as they are being produced. They are specialized for one task and division is not one of them. Their primary job is to aid in the exchange of gasses in the lungs and in the large number of different organ systems throughout the body.
How Are RBCs Produced?
Stem cells in the bone marrow can produce red blood cells (RBCs) or white blood cells (WBCs). The cells designated to become RBCs are programmed to make large quantities of hemoglobin, a protein in those cells that transports oxygen in the blood.
In addition, these pre-programmed cells lose their nuclei and cell manufacturing machinery as they change into an RBC. By the time an RBC is fully mature, it is packed mostly with hemoglobin and some enzymes. It also assumes its flat and rounded disk shape as it enters the circulation.
Where Are RBCs Produced?
RBCs begin their development from stem cells in the bone marrow. When they leave the bone marrow, they are not fully mature, although they have lost their nuclei and can perform their primary function of gas exchange.
The final phases of RBC maturation take place in the spleen. Specialized WBCs in the spleen remove the last bits of unnecessary material from inside the RBCs. After that, the fully mature RBCs leave the spleen to go to the heart and begin exchanging gases in body tissues.
How Often Are RBCs Produced?
Red blood cells are produced constantly. Normally about two million RBCs are made each second. That number seems large, but because RBCs are very small, the volume of all those cells would be less than a drop of water.
The number of cells that can be made can change depending on signals from the brain and endocrine system, which includes the glands in the body that create and release hormones.
For example, if you donate a pint of blood your body responds by signaling stem cells in the bone marrow to increase the rate of RBC production to replace the cells that have been lost. This does not happen right away, however, because it can take up to two days for a mature RBC to be produced.
How Long Do RBCs Live?
On average, a RBC lives for about 120 days. During that period, they are very busy. An RBC spends most of its time in the capillary beds (the network of blood vessels) of the body’s various organs, crawling along at roughly one inch per second.
RBCs move relatively quickly to and from the heart, through veins and arteries respectively. Once a red blood cell is in the left ventricle (bottom left portion) of the heart, it is launched into the arterial circulation and reaches its destination in the body’s organs quite randomly, returning to the right side of the heart through the veins, about one minute later.
Because there are nearly 60,000 miles of blood vessels (mostly small capillaries) in the human body, it is unlikely that a red blood cell will live long enough to travel through every single blood vessel, but it will likely visit every organ system several times over.
RBCs become less effective over time. Specialized white blood cells in the spleen, bone marrow, and liver recognize these older blood cells and destroy them. In the bone marrow, some of the contents of the spent red blood cells are recycled to create new RBCs.
Tests for Red Blood Cells
Patient Power asked George D Lundberg, MD, a leading academic pathologist, medical journalist, and current Editor in Chief of Cancer Commons based in Los Gatos, California, about the various tests that may be done to measure RBCs.
He explained, “RBCs, hemoglobin, and hematocrit are all measures of the same thing: how well the blood is equipped to transport oxygen from the lungs to all tissues, and carbon dioxide from all the tissues to the lungs. Hemoglobin is within the RBCs and can be chemically measured; the RBCs can be counted; and the hematocrit is the percentage of actual blood that is physically composed of RBCs.
In rare forms of blood cancer, these numbers may increase. In most patients with cancer, these numbers are stable unless bleeding occurs, or the cancer invades bone marrow.”
Expected Results for Tests of Red Blood Cells
What about usual or expected RBC values? Dr. Lundberg explained that “so-called ‘normal’ is a statistical reference range determined by testing large numbers of individuals. Each person is an individual and may carry different, but consistent, numbers over a lifetime. A ‘normal’ adult RBC ranges from 4,000,000 to 5,900,000 per cubic millimeter for men and 3,800,000 to 5,200,000 per cubic millimeter for women. A ‘normal’ adult (men and women the same) range for WBCs is 5,000 to 10,000 per microliter of blood.”
So when should people living with cancer worry about their results? Dr. Lundberg replied, “Assuming the patient does not have a blood cancer, worry is reasonable when either RBCs or WBCs change substantially from the patient's normal – RBCs lowering and WBCs either lowering or elevating, depending on potential complicating conditions.” He went on to explain that, “since blood cancers involve the white cells and may involve the red cells as part of the cancer, the ups and downs of numbers vary all over the place, depending on blood cancer types and stages. This may reflect good or bad news, on a case to case basis.”
He also pointed out that “sometimes a low amount of hemoglobin can be an early sign of cancer, such as cancer in the colon where silent bleeding may deplete hemoglobin.” The best advice is to talk to your physician about your own unique situation.
What Affects RBC Production?
Because RBCs contain mostly hemoglobin, anything that disrupts the way that cells manufacture this vital blood protein can affect the production of the cells themselves. Diet is one important factor.
For example, hemoglobin contains iron, and since the body can’t manufacture this mineral, it must be obtained from diet. Copper is another mineral essential for hemoglobin production. Vitamins such as B6 and B12 assist the many enzymes that must work properly to produce functional RBCs. Do let your physician know if you are taking supplemental vitamins, iron, or other minerals.
In addition, stem cells and WBCs that are important in the development, maturation, and destruction of RBCs. The WBCs must function effectively to ensure that RBCs are healthy and that their numbers are within an acceptable range.
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Susan Yox is a nurse and health educator who has worked as a writer, editor, and most recently, as Director of Editorial Content at Medscape, a website for physicians, nurses, and other healthcare professionals.In addition to a BS and MS in nursing, she holds a doctorate in Health Behavioral Sciences.Susan writes for health professionals and consumers, often focusing on infectious diseases, public health, oncology, and nursing.
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