Chewing starts digestion by breaking food into smaller pieces mixed with saliva.

The longer version

Mastication breaks food into fragments and multiplies the surface area exposed to digestive enzymes, so later chemical steps work faster. The jaw muscles can generate considerable force at the back teeth, while the front teeth cut and tear.

As the pieces are crushed, saliva is mixed through them, and the resulting softened mass can be shaped and pushed to the back of the mouth for swallowing. Chewing also stimulates glands further along the digestive tract, which begin preparing secretions before food arrives. Sensation from the teeth and jaw feeds back to control the force, protecting the tooth and the tongue. Swallowing then takes over as a largely automatic sequence that closes off the airway.

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.