DORA: Ooooh--I've got a scab here. What IS a scab, anyway?
WENDELL: Did you hurt yourself, Dora?

DORA: Yup.
WENDELL: Well, Dora, a scab is just the dried blood bandage that your body made to protect the cells underneath it until they repair themselves.

DORA: That's cool, Wendell!
WENDELL: Yup. Scabs are very cool, Dora!

DORA: How'd my body make this scab?
WENDELL: When you scraped your elbow, your skin was broken. First to arrive on the scene of the accident were special blood cells called platelets.

DORA: What did they do, Wendell?
WENDELL: It's an extraordinary story. Normally, your blood is thin and flows easily through blood vessels, right?

DORA: Right!
WENDELL: Well, when platelets discover that there has been damage to a part of the body, they start to change. A chemical protein inside them causes them to become sticky -- and thick like pudding. Soon, a sticky plug or clot has stopped the blood from leaking.

DORA: That's a relief! What else happens?
WENDELL: First, a variety of other chemicals work to dry up the blood and turn the plug into a dry scab, which acts as an emergency patch.

DORA: How does my skin heal itself?
WENDELL: With the emergency patch in place to keep out germs, the fiber-making cells underneath attach the plug to the surrounding skin and one end of the scraped skin to the other.

DORA: All this is happening on my elbow?
WENDELL: That and more. Underneath, new skin cells are manufactured; ripped blood vessels begin to mend and blobby-shaped white blood cells get busy for a big marathon meal! They eat up any germs that sneak in, but, primarily, they gobble up, like a vacuum cleaner, all the dead blood and skins cells that remain at the site of the scrape.

DORA: Uh-oh! I think I see pus. How does pus get here?
WENDELL: Don't worry. Pus is just a whitish-yellow, slightly putrid liquid containing piles of dead debris: dead cells and dead bacteria, and even some white blood cells that died while gobbling. The pus is being pushed out by the rest of tissue and will drain off.

WENDELL: Now, Dora, don't pick at that scab or you may rip the lovely new skin underneath! Pretty soon, when all the repair work has been done, your scab will just fall right off!
DORA: I can't wait!