Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.
Red Blood Cells and Hemoglobin
We previously learned that red blood cells, or erythrocytes, are the most common type of blood cell. Their primary function is to carry oxygen to the body tissues via the circulatory system. Red blood cells are perfectly designed to perform this oxygen-carrying function, and in this lesson, you will learn more about what makes your red blood cells so good at their job. You will also discover what happens when the oxygen-carrying ability of the red blood cell is compromised.
The reason mature red blood cells are so good at carrying oxygen is because they make room by eliminating their nucleus. That's right - an immature red blood cell has a nucleus that allows it to reproduce, but when it matures, this nucleus disappears, making more room for hemoglobin. Hemoglobin is the oxygen-carrying pigment of the red blood cell. To help recall this term, it's good to note that 'heme' refers to 'blood' and 'globin' refers to 'protein' - so hemoglobin is a blood protein. Each iron-containing hemoglobin molecule is responsible for transporting the bulk of oxygen through your blood, and, interestingly, it's hemoglobin bound to oxygen that gives your blood its bright red color.
We know that red blood cells are plentiful, and although their numbers are important, it's the amount of hemoglobin that they carry that determines how efficiently oxygen will circulate through your body. The more hemoglobin molecules found within your red blood cells, the more oxygen they will be able to transport. A decrease in the oxygen-carrying ability of the blood results in a condition called anemia. This can be due to a decreased number of red blood cells or a decreased amount of hemoglobin. Anemia is an easy term to recall if you remember that the prefix 'an' refers to 'without' or 'lacking' and 'emia' refers to 'blood,' so 'anemia' literally means 'without' or 'a lack of' 'blood.'
There are a few things that can cause a decrease in the number of red blood cells. One way that seems the most obvious is a massive loss of blood or a hemorrhage. Hemorrhagic anemia is anemia due to an excessive loss of red blood cells through bleeding. This blood loss may be caused by a wound, but it can also result due to something going on internally, such as a stomach ulcer or heavy menstrual bleeding.
Blood cells do not have to be lost to cause anemia. Sometimes there's a problem with their production. Red blood cells are formed in the bone marrow, which we previously learned is the connective tissue that fills the cavities of bones and is the chief site for red blood cell formation. Destruction or inhibition of the red bone marrow results in aplastic anemia, which is defined as a disorder in which the bone marrow fails to make enough blood cells. You can recall this term by noting that 'aplastic' means 'failure to develop.' Therefore, it's an anemia that's due to the failure of blood cells to develop. Aplastic anemia is a serious condition, and it can develop at any age. The cause might not be known, or it could result from radiation or chemotherapy treatment or exposure to toxins or medications.
Pernicious anemia is another type of anemia that involves a decrease in the production of red blood cells, but unlike aplastic anemia that involves the bone marrow, pernicious anemia involves the absorption of vitamin B12. Therefore, we define pernicious anemia as a disorder in which the body cannot make enough red blood cells because the intestines cannot properly absorb vitamin B12. Your body needs vitamin B12 to make red blood cells. Vitamin B12 is a nutrient found in certain foods that you eat, such as meat, poultry, shellfish, eggs and dairy products. People who have pernicious anemia can't absorb enough vitamin B12 from these foods because they lack intrinsic factor. Intrinsic factor is a special protein made in your stomach that helps your intestines absorb vitamin B12. When your stomach does not make enough intrinsic factor, the intestine cannot properly absorb vitamin B12. Interestingly, the word 'pernicious' means 'deadly.' Even though pernicious anemia is usually easy to treat with today's modern medical advancements, when it was first discovered, this form of anemia would often result in death, hence the name.
Sickle Cell Anemia
Anemia can sometimes result due to a genetic disorder, which is the case with sickle cell anemia. Sickle cell anemia occurs almost exclusively in black people of African descent. It is described as a severe hereditary form of anemia in which the red blood cells are sickle-shaped due to an abnormality in their hemoglobin. Normally, red blood cells are round and flexible, which helps them squeeze through tight capillaries without getting stuck. In the case of sickle cell anemia, however, some of the red blood cells become stiff and sickle-shaped. The abnormal shape and stiffness of the sickled red blood cells makes them more likely to get stuck in the blood vessels and cause blockage that can result in severe pain and organ damage. These abnormal sickle-shaped cells only circulate for about 10-20 days instead of the typical 120 days or so. The body cannot make enough red blood cells to keep up with this pace and this rapid turnover, and so the result is anemia.
Let's review. Hemoglobin is the oxygen-carrying pigment of the red blood cells. If there's a decrease in the amount of red blood cells or hemoglobin, it can cause a decrease in the oxygen-carrying ability of the blood, which is a condition called anemia.
One way you could lose red blood cells is through a massive loss of blood or a hemorrhage. This results in hemorrhagic anemia, which is defined as an anemia due to an excessive loss of red blood cells through bleeding.
Anemia is not always due to the loss of blood cells; it can be due to a drop in the production of red blood cells, such as in the case of aplastic anemia. Aplastic anemia is defined as a disorder in which the bone marrow fails to make enough blood cells.
A decrease in the production of red blood cells can also result due to problems with absorption of vitamin B12. We define pernicious anemia as a disorder in which the body cannot make enough red blood cells because the intestines cannot properly absorb vitamin B12. Your body needs vitamin B12 to make red blood cells, and it needs intrinsic factor in order to absorb vitamin B12. Intrinsic factor is a special protein made in the stomach that helps your intestines absorb vitamin B12.
Anemia can sometimes be the result of a genetic disorder, which is the case with sickle cell anemia. Sickle cell anemia is a severe hereditary form of anemia in which the red blood cells are sickle-shaped due to an abnormality in their hemoglobin.
After watching this lesson, you should be prepared to:
- Define hemoglobin, anemia and intrinsic factor
- Name and describe the different types of anemia
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