Anemia: Types and Causes

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  • 0:05 Red Blood Cells and Hemoglobin
  • 1:17 Anemia
  • 1:59 Hemorrhagic Anemia
  • 2:21 Aplastic Anemia
  • 3:07 Pernicious Anemia
  • 4:15 Sickle Cell Anemia
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Your red blood cells have a unique design that differentiates them from all other cells. This unique design makes them exceptional oxygen carriers. But if this ability to carry oxygen is compromised, the result is a form of anemia, such as pernicious anemia, aplastic anemia or sickle cell anemia.

Red Blood Cells and Hemoglobin

Mature red blood cells have no nucleus, making more room for hemoglobin.
Red Blood Cells No Nucleus

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.'

Hemorrhagic Anemia

Red blood cells are formed in bone marrow.
Red Blood Cells Made in Bone Marrow

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.

Aplastic Anemia

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.

Intrinsic factor is a protein that aids the intestines in absorbing vitamin B12.
Intrinsic Factor Needed to Absorb B12

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