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Red Blood Cells and Hemoglobin in Health and in Anemia Disorders

Updated on January 06, 2017
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Linda Crampton is a teacher with an honours degree in biology. She enjoys writing about human biology and the science of health and disease.

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Red blood cells
Red blood cells | Source

The Importance of Red Blood Cells and Hemoglobin

Red blood cells, or erythrocytes, are extremely important cells that are abundant in our blood and have vital functions in our bodies. They transport oxygen from our lungs to our tissue cells and are also involved in transporting carbon dioxide waste in the opposite direction. The oxygen is attached to a red pigment in the erythrocytes called hemoglobin. Each of the many trillions of cells in our bodies needs the oxygen delivered by the blood to survive and to do its jobs.

A problem with red blood cells or with hemoglobin will affect our health and can cause many different symptoms. The effects of the problem may be minor or they may be more serious. Anemia is the general name given to conditions in which there are not enough healthy red blood cells in the blood or in which there is abnormal hemoglobin in the cells. Four of these conditions are iron deficiency anemia, pernicious anemia, sickle cell disease, and thalassemia.

What Does Blood Contain?

A red blood cell or erythrocyte is pale red in colour. It looks likes a doughnut with a hole that hasn't been completely punched through its centre.

Production of Red Blood Cells

Bone marrow is found inside bones. Red blood cells are made in red bone marrow. Yellow bone marrow contains many fat cells and is unable to make erythrocytes.

Red marrow is found inside every bone of a baby at birth. As we age, some of this marrow is converted into the yellow type. In adults, red marrow is found in the breastbone (sternum), the ribs, the shoulder blades, the vertebrae, the skull, and the pelvis. It's also found at the ends of the long bones in the arms and legs. The shafts of the long bones contain yellow bone marrow. In cases of extreme blood loss, yellow marrow can be converted into the red kind so that more erythrocytes can be made.

Erythrocytes and Anemia

Red Blood Cell Facts

  • A red blood cell has the shape of a circular disk.
  • The cell is thinner in the middle than at the edge.
  • A mature red blood cell contains no nucleus.
  • There are about 4 to 6 million erythrocytes in each cubic millimetre of blood.
  • Men have more erythrocytes than women.
  • People living at high altitudes, where there is less oxygen in the air, have more erythrocytes than people living at lower altitudes.
  • 20 to 60 seconds are needed for a particular red blood cell to circulate around the body.
  • The smallest blood vessels, called capillaries, are so narrow that red blood cells have to be deformed in order to squeeze through them.
  • An erythrocyte lives for about 120 days.
  • Every second the red bone marrow makes about 2.5 million erythrocytes.
  • About the same number are broken down each second.
  • Old and damaged erythrocytes are broken down by the spleen and the liver.

Substances such as oxygen and nutrients leave a capillary and enter the interstitial fluid around cells. Substances such as waste move in the opposite direction.
Substances such as oxygen and nutrients leave a capillary and enter the interstitial fluid around cells. Substances such as waste move in the opposite direction. | Source

Erythrocyte Functions

Erythrocytes contain molecules of a red protein called hemoglobin (or haemoglobin). The hemoglobin molecules give the cells their colour and contain iron. The iron joins with the oxygen that we inhale.

The erythrocytes transport the oxygen around the body, delivering it to all the body’s cells. These cells use the oxygen to produce energy. After releasing the oxygen, hemoglobin molecules join to carbon dioxide, which is a waste product made by cells. The erythrocytes then carry the carbon dioxide to the lungs to be exhaled. A small amount of carbon dioxide dissolves in the blood plasma (the liquid portion of blood) and is transported to the lungs in this form.

There is a third method of carbon dioxide transport to the lungs, which is actually the most common way to get rid of the chemical. Red blood cells contain an enzyme called carbonic anhydrase. This enzyme triggers the carbon dioxide made by cells to react with water. Hydrogen ions and bicarbonate ions are made as a result. The hydrogen ions join to the hemoglobin molecules. The bicarbonate ions enter the blood plasma.

In the lungs, the above reaction is reversed. The hydrogen ions carried by the hemoglobin molecules and the bicarbonate ions in the blood plasma react to make carbon dioxide and water, which are exhaled.

Normal and abnormal red blood cells as seen under a microscope; the spiky ones are present in certain diseases and are called acanthocytes
Normal and abnormal red blood cells as seen under a microscope; the spiky ones are present in certain diseases and are called acanthocytes | Source

Iron Deficiency Anemia

The most common form of anemia is known as iron deficiency anemia. In this disorder there isn't enough iron available for making new hemoglobin, so the red blood cell count or the amount of hemoglobin in the blood is lower than normal.

Iron deficiency anemia can be caused by loss of red blood cells due to bleeding, increased need for iron during rapid growth phases or during pregnancy, inability to absorb iron due to small intestine damage, as in celiac disease, or the break down of too many red blood cells (hemolysis). Hemolysis can be caused by the malaria parasite, certain bacterial infections and other triggers.

A photo of blood cells made with a scanning electron microscope; the red blood cell is on the left, an activated platelet is in the middle and one type of white blood cell is on the right
A photo of blood cells made with a scanning electron microscope; the red blood cell is on the left, an activated platelet is in the middle and one type of white blood cell is on the right | Source

Symptoms of Iron Deficiency Anemia

The main symptoms of iron deficiency anemia are tiredness and weakness. There may also be a range of other symptoms, including:

  • pale skin
  • shortness of breath
  • dizziness
  • headache
  • feeling faint
  • heart palpitations
  • brittle nails
  • a sore tongue
  • a craving for strange foods, such as ice or dirt (a condition known as pica)

As in any form of anemia, it's important to get a doctor's diagnosis and treatment advice if symptoms appear.

Common treatments for iron deficiency anemia include dealing with any health problems that are causing the illness, receiving iron injections or supplemental iron and making dietary changes. If you suspect that you have the condition, don’t take supplements without seeing a doctor. Too much iron in the body can be dangerous.

What is Pernicious Anemia?

Pernicious Anemia Facts

In pernicious anemia, a person’s body is unable to make intrinsic factor. Intrinsic factor is made by cells lining the stomach. It binds with vitamin B12 to enable it be absorbed in the small intestine. Vitamin B12 is needed to make hemoglobin, so people with pernicious anemia can't make enough hemoglobin and don't make enough normal red blood cells.

People with all forms of anemia suffer from tiredness and may also experience shortness of breath, heart palpitations, dizziness, headache and pale or yellowish skin. In addition, people with pernicious anemia may develop a thick, smooth and red tongue. Severe vitamin B12 deficiency can cause neurological (nerve) problems. These may include numbness, tingling, muscle weakness, balance problems, difficulty in walking, confusion, and memory loss. There may be digestive problems as well, including nausea, vomiting, and heartburn.

Intrinsic factor is made in the stomach and binds to vitamin B12. The vitamin is absorbed in the small intestine.
Intrinsic factor is made in the stomach and binds to vitamin B12. The vitamin is absorbed in the small intestine. | Source


The word "pernicious" means "deadly". Pernicious anemia used to be fatal but is easily treated today. It's important to visit a doctor if you have any of the symptoms of pernicious anemia, though. A doctor will make a diagnosis and prescribe treatment.

Pernicious anemia is treated with vitamin B12 injections or high dose vitamin B12 pills, depending on the severity of the condition. Sending the vitamin into the body via injection bypasses the need for intestinal absorption. Some vitamin B12 is absorbed through the intestinal lining without intrinsic factor via a process called passive diffusion. When someone ingests a large dose of vitamin B12, their intestine may be able to absorb enough of the vitamin to fulfil their body's needs. The decision as to whether this actually happens must be made by a doctor.

What Is Sickle Cell Disease?

Sickle Cell Disease Facts

In sickle cell disease or SCD, the red blood cells are shaped like a crescent instead of being round, especially when they contain a low amount of oxygen. The cells contain an abnormal form of hemoglobin. Sickle cell anemia is the most common form of SCD.

Sickled red blood cells are unable to flow through the blood vessels easily and are sticky. If they stick to each other they may interfere with the flow of blood and oxygen. They don't live as long as normal red blood cells and die after 10 to 20 days.

People with sickle cell disease have at least one gene for an abnormal form of hemoglobin known as hemoglobin S. The abnormal hemoglobin causes their red blood cells to sickle. If a person has two genes coding for hemoglobin S, they are said to have sickle cell anemia. This is the most common and the most severe form of SCD.

Living With Sickle Cell Disease

Symptoms of SCD

Symptoms of SCD include typical anemia symptoms as well as an experience called a sickle cell crisis, which may happen periodically. During this crisis, the abnormal red blood cells block small blood vessels. This interferes with the blood flow to nearby tissues, damaging the cells in the area. In addition, the tissues become swollen and press on nerves, causing pain. Pain-relieving medications can help this situation.

Sometimes a sickle cell crisis occurs for no apparent reason, but some sufferers can link it to a particular trigger, such as dehydration, exercise or a sudden change in body temperature. In these cases avoiding the potential trigger can be very helpful.

Thalassemia: A Cartoon Explanation for Children (and Adults)

Thalassemia Facts

The term thalassemia or thalassaemia refers to a group of inherited disorders in which the body has trouble making normal hemoglobin. This results in a reduced number of red blood cells or in red blood cells that are smaller than normal.

Hemoglobin is a complex molecule. Several genes control its production. The symptoms and seriousness of thalassemia depend on which of the hemoglobin genes are mutated (altered) and on how many of them are mutated. Mild forms of thalassemia may not produce any symptoms and may not need medical treatment. Dealing with the serious forms of thalassemia can be challenging, but treatments are improving.

In addition to typical anemia symptoms, people with thalassemia may experience jaundice (yellow skin), an enlarged liver or spleen, and enlarged bones, particularly in the face.

Treatments for severe thalassemia include regular blood transfusions. Frequent blood transfusions cause iron to build up in the body as the red blood cells break down, which is dangerous. A process called chelation is used to remove the excess iron. Some thalassemia patients are prescribed folate supplements.

It's very important that people with any form of anemia visit their doctor regularly. The doctor will be able to recommend the most appropriate treatments for the patient's problems and also monitor their condition. In addition, a doctor will know about new or alternate treatments that are available.

References and Further Information

Iron Deficiency Anemia from the Merck Manual

Pernicious Anemia from the National Heart, Lung and Blood Institute

Sickle Cell Disease (or Sickle Cell Anemia) from the U.S. National Library of Medicine

Thalassemia from the Centers for Disease Control and Prevention

© 2010 Linda Crampton


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    • Ingenira profile image

      Ingenira 5 years ago

      Comprehensive information on red blood cells.

      I am surprised to know that people living at high altitudes, where there is less oxygen in the air, have more red blood cells than people living at lower altitudes. I wonder whether they will have problem when they move to places at low altitudes ?

    • AliciaC profile image

      Linda Crampton 5 years ago from British Columbia, Canada

      Thanks for commenting, Ingenira. Researchers have found that when people who have been living at high altitude travel to a place at low altitude, their red blood cell concentration gradually decreases.

    • profile image

      kp 4 years ago

      Why is the red blood cell number in males more than in females?

    • AliciaC profile image

      Linda Crampton 4 years ago from British Columbia, Canada

      Hi, kp. Testosterone in males stimulates red blood cell production, giving them a higher red blood cell count.

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