Saliva keeps the mouth moist and begins breaking down food before swallowing even starts.

The longer version

Saliva contains enzymes that begin attacking starch while food is still being chewed, splitting long chains into smaller sugars. It also carries mucus that lubricates the mouth and binds chewed fragments into a lump easy to swallow.

The fluid is mostly water, supplied by several glands, and it includes compounds that buffer acid and help keep tooth mineral intact. Production rises before and during a meal through a reflex triggered by taste and by the act of chewing itself. Saliva also dissolves flavour molecules, which is why dry food tastes faint until it mixes with it. Its flow slows during sleep, which is one reason the mouth feels dry in the morning.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.