Sickle Cell Anemia: Definition & Explanation

Instructor: Kelly Robson

Kelly has taught High School Science and Applied Communications. She holds an Education Specialist Degree in Ed. Leadership.

In this lesson, you will learn about sickle cell anemia, an inherited disease where some of the red blood cells are deformed and cause the patient painful and debilitating issues.

What is Sickle Cell Anemia?

The disease sickle cell anemia explains itself in its own title. Sickle describes the shape, or in this case, the misshape of the cell. When the cells take the shape of sickles, which also look like crescent moons, they don't function properly. They make it so patients are unable to replace their blood in a timely fashion. This lack of blood is also called 'anemia.' Therefore, sickle cell anemia could also be translated as 'misshaped blood cells that cause a lack of blood.'

Structure and Function

The human body is a remarkable piece of work in which every part has its own function. Each part has a specific structure to best fit its function. When everything is structured (shaped) properly, it should function properly. However, there are many times when parts of the body are misshaped, and the deformed structure no longer allows for the body to function properly.

The function, or job, of red blood cells is to carry oxygen to all the organs in the body. They also get rid of the carbon dioxide (CO2), a poison in our bodies. They travel through a maze of blood vessels such as veins and arteries. To make for smooth travel through the body, normal red blood cells are shaped like little flexible disks. Their shape allows for them to bend and twist and move around the body in a smooth, fluid movement. Blood cells shaped like sickles can obviously not perform their function as well.

A Protein Called Hemoglobin

All red blood cells have a protein in them called hemoglobin (HEE-muh-glow-bin). Hemoglobin is what attaches the oxygen to the cell. A person with sickle cell anemia has some red blood cells that have a different kind of hemoglobin called hemoglobin S. Hemoglobin S causes a red blood cell to be deformed into a sickle shape. A sickle cell is stiff and sticky instead of smooth and flexible.

Normal and sickle red blood cells
Photo of Sickle Cells

Since a sickle cell is stiff and sticky, it is not able to travel through the vessels as well as it is supposed to. This can create blockages in the vessels which can lead to severe pain or organ damage. When a person is experiencing this extreme pain, it is called an episode. These episodes can last for hours or even days. During some episodes, a patient should stay in the hospital.

Diagram of sickle cells and blood vessels

Another issue resulting from sickle cell anemia is the life cycle of the blood. Red blood cells are made in the large bones of the body and are replaced about every 120 days. A sickle red blood cell only lives for about 10-20 days. Therefore, the body cannot replenish the blood in time and it causes a shortage of blood otherwise known as anemia. Since these cells are made in the large bones of the body, a patient can have episodes in these bones causing extreme pain.

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