In this topic you will learn how special parts of your body help you use food as fuel for energy.

Food can be broken down into smaller pieces by being crushed and cut. Crushing and cutting is part of digestion. Digestion is the process of breaking down food.

Digestion begins in your mouth. When you put food in your mouth, you taste it with your taste buds. Taste buds are thousands of cells on your tongue that send signals for sweet, sour, bitter, and salty to your brain. Most foods contain a mixture of tastes.

When you put food in your mouth, saliva pours into it. Saliva is a liquid in your mouth that helps soften and break down food. Saliva is released by the salivary glands.

Your teeth bite, slice, and tear solid food to pieces. They crush, grind, and chew it. The longer you chew your food, the smaller the pieces get. Smaller pieces are easier to swallow and digest.

When you swallow, food moves down the esophagus. The esophagus is a tube that carries food to the stomach. The stomach is part of your body with walls made of strong muscles that squeeze and mash food. Your stomach stretches to hold all the food you swallow. After two to four hours, the food has changed into a thick, soupy mixture. Little by little, your stomach muscles squeeze this mixture out of your stomach and into your small intestine.

Your small intestine is a tube-like part of your body where most digestion takes place. The small intestine finishes breaking down the food. The digested nutrients go out of your small intestine and into your blood. Not all food is broken down during digestion. Undigested parts of the food, such as fiber, are moved from your small intestine into your large intestine. Your large intestine is the part of the body that removes water from undigested food. The solid waste that is left is pushed along until it leaves the body.