"I spat on the ground as I begun to preform life saving CPR techniques on my friend as he went into cardiac arrest."
Your saliva consist of 98% water and 2% of mucus, electrolytes, antibacterial compounds and enzymes. That magical two percent practically protects your mouth from 95% of the things you throw at it. Producing saliva can account for digesting your food and lubricating your tongue, teeth and soft tissues in your mouth. Not only that, but it also pays a vital role to tasting food. Without saliva, that delicious red velvet cake would be nothing but a soft, luxurious, tasteless cake.
The saliva in your mouth isn't simply sitting there waiting for food, it's constantly breaking down and killing microbes in your mouth. Any small bits of food stuck between your teeth can be broken down easily along with any bacteria that decides to call your mouth home. That mixture of liquids inside your mouth is working day and night to make sure mold and fungus doesn't simply grow inside of your mouth on your daily basis.
You wouldn't want these growing in your mouth, would you?
A perfect example of your saliva in action, or in-action is during the night. When you sleep, your body doesn't produce as much saliva as you do when you're awake. So during that time period, bacteria and other microbes are free of those pesty antibacterial compounds and are free to grow. You may have noticed that when you wake up your mouth is as dry as a desert and your breath smells like death itself, which is a result of your saliva in in-action.
The reason you need to brush your teeth in the morning, is to brush and scrub those bacteria away and to give your saliva a head start to re-claim your mouth. If you forget to brush your teeth on a Monday or something, you may have noticed that later on the day, your bad breath eventually goes away and your mouth feels fine, your saliva finally brought bacteria levels to the normal level. (But that doesn't mean you should stop brushing your teeth.)
Unless you really like cavities.
Not only does your saliva fight bacteria and be awesome, but it can help fight against cavities and tooth decay. When you eat sugary candies, you practically give the bacteria in your mouth another weapon against their arch nemesis, you. After digesting your sugars, the bacteria turns the sugars to acids which along with other food particles and bacteria, cling on to teeth to form plaque. Soon enough, the acid is given direct access to your teeth which allows the acid to dissolve your enamel and begin to create holes for more plaque to grow.
Your saliva plays a large role in preventing plaque from even forming in the first place. Not only does saliva fight the bacteria that form the acids, but it can actually neutralize the acids with it's base pH. Along with breaking down small food particles and diluting sugars, it's a one hit wonder. In more direct cases, such as drinking pure lemon juice, your saliva is one of those unsung heroes that prevent your stupidity from killing you.
Your saliva ain't getting you out of this pickle.
But there's other ways that saliva help you too. More obvious ones would be lubrication for food; have you ever tried eating sixteen saltine crackers? It's pretty hard after your saliva's gone right? All in all, it's like oil for your car, you don't really think about it until you run out of it.