Pull a lollipop out of your mouth and you'll see it. Wake up after drooling on your pillow and you'll feel it. That's right, it's spit, also known as saliva (say: suh-lie-vuh).
Saliva is a clear liquid that's made in your mouth 24 hours a day, every day. It's made up mostly of water, with a few other chemicals. The slippery stuff is produced by the salivary (say: sah-luh-vair-ee) glands. These glands are found on the inside of each cheek, on the bottom of the mouth, and under the jaw at the very front of the mouth. They secrete (say: sih-kreet), or ooze, about 2 to 4 pints (or about 1 to 2 liters) of spit into your mouth every day!
Spit is super for lots of reasons. Saliva wets food and makes it easier to swallow. Without saliva, a grilled cheese sandwich would be dry and difficult to gulp down. It also helps the tongue by allowing you to taste. A dry tongue can't tell how things taste — it needs saliva to keep it wet.
Spit helps begin the process of digestion (say: dy-jes-chun), too. Before food hits your stomach, saliva starts to break it down while the food's still in your mouth. It does this with the help of enzymes (say: en-zimes), special chemicals found in the saliva. The combination of chewing food and coating it with saliva makes the tongue's job a bit easier — it can push wet, chewed food toward the throat more easily.
Saliva also cleans the inside of your mouth and rinses your teeth to help keep them clean. (But remember that spit isn't enough to keep teeth in tip-top shape; you still need to brush and floss!) The enzymes in saliva also help to fight off infections in the mouth.
Most school-age kids have just the right amount of saliva. Sometimes a person may not have enough saliva, but this is usually the result of certain medicines or treatments, some kinds of diseases, or old age.