Dear Liam,

Did you know your skin is the largest organ in your body? The average 5th grader has more than 6 pounds of skin. Whoa.

Skin protects the inside of your body from the dirty outside world. It keeps your insides from drying out and ensures a steady body temperature. It lets you feel things you touch.

Your skin also has the incredible ability to heal itself. I talked about that with my friend Edward Johnson. He teaches classes about the human body in the School of Biological Sciences at Washington State University.

“Skin is the point of contact between you and everything in your environment,” Johnson said. “So, it’s evolved the ability to regenerate.”

Your skin is made of two layers stacked together. The outer layer is the epidermis. It’s made of epithelial cells. These cells line the inside and outside of your body. They also line your organs.

Below the epidermis is the dermis. It’s made of connective tissue. That’s tissue that holds your body together—like tendons and ligaments. Bone and blood are connective tissue, too.

When you cut your skin, the damaged cells release signaling molecules. It’s like setting off an alarm that tells other cells, cell fragments called platelets and proteins to rush to the injury.

If your cut is bleeding, platelets and proteins in your blood zoom to the rescue. They plug up the damage with a clot to stop the bleeding. When the clot dries out, it’s called a scab.

Bacteria and viruses can get into your body through a wound. So, signaling molecules also send the alarm to white blood cells from your immune system. Their job is to kill and gobble up microbes near the cut.

Then, signaling molecules tell the connective tissue to start making new cells. The new cells—called granulation tissue—fill in the cut. Granulation tissue looks pink or red and a bit bumpy or lumpy.

“Granulation tissue is brand new connective tissue plus all the blood vessels,” Johnson said. “It basically starts at the bottom of the cut and fills up the cut to repair it. It’s like puttying up a crack in a wall.”

As the wound fills up with granulation tissue, the edges of the cut pull together and begin to close. Then, your body lays down a new layer of epithelial cells on top of the granulation tissue.

For many cuts, the healing process takes a few weeks. But it can take much longer for the wound to heal completely. Sometimes you’ll see a scar where the cut healed, especially if the cut was deep.

Keep the wound clean and look for signs that you need to show it to a healthcare provider—like if the wound becomes red and warm, oozes yellow fluid or if you start to feel sick.

That’s the best way to take care of the skin that takes care of you.


Dr. Universe