Saliva is a watery, frothy substance that your mouth manufactures continuously. It trickles out through glands scattered around your mouth, cheeks, and throat, but most of it seeps up from under your tongue. You produce a small milk-carton’s worth (1 liter) of the stuff every day, most obviously when you eat, and hardly at all when you sleep.
Saliva cleans your teeth, lubricates your mouth, and protects the tender tissues inside. It also dissolves the substances in your food so they can reach your taste buds. In fact, without saliva, your favorite meal would be as appetizing as a stick of chalk.
Saliva also contains enzymes that start breaking down the long chains of complex carbohydrates in your food. (Enzymes are special compounds your body builds and then uses to carry out complex chemical reactions, like digestion.) For example, in the breakfast meal you’re chewing right now, enzymes split some of the starches in your toast. It’s all a bit of a preview to the heavy-duty digestion that takes place lower down the digestive tract. Saliva also moistens your food so your teeth can compact it into a small, soggy ball that’s ready to shoot down your throat and into your stomach.
Once your teeth and salivary glands have done their work, it’s time to swallow hard and move on. Your meal has now entered the winding passages of your digestive tract, where it will remain for the rest of its journey.
Although saliva includes its own natural antibacterial agents, opinions differ about whether the distinctly icky practice of licking wounds is healthy or dangerous. One thing is certain: Putting your tongue to a cut introduces not just antibacterial substances, but a huge family of mouth-dwelling bacteria, too—some of which can cause real trouble if they make their way deeper into your body.
Source of Information : Oreilly - Your Body Missing Manual