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You may know that your skin is made of cells, your bones are made of cells, and your blood is made of cells. But these cells aren't all the same types of cells. Different types of cells each do unique jobs in your body. Together, they let your body function as a whole. So to put it in a joke format, how many types of cells does it take so that an adult human can screw in a light bulb? Any guesses? Over 200.
There are about 200 different types of cells in your body. These cells make up your organs and tissues, as well as help to defend your body as a part of your immune system. Your cells are constantly being replaced as they die.
For example, the skin cells on the surface of your body live for about 30 days and then are replaced as they fall off. When red blood cells are old and need to be replaced, they are filtered out of your blood in the spleen, and new red blood cells are made in your bone marrow to replace them.
As cells get old and die, they are replaced, so your body is always made up of healthy living cells. Some dead cells stick around too, making up the outer layers of your skin, your fingernails, and your hair.
Looking for the number of total cells in the human body? Visit Building Blocks of Life.
Interested in immune cells? Don't miss Viral Attack.
cell image by Nephron via Wikimedia Commons
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