How digestion changes food — Health, 7–10 years
Food cannot travel into your blood in the form of a sandwich or an apple. Digestion breaks it into tiny useful parts that the body can absorb.
A long food journey
Digestion begins in the mouth, where teeth break food up and saliva softens it. The food then travels through the stomach and intestines, where it is mixed with digestive juices, broken into smaller parts and absorbed into the blood.
Why must food be broken down?
A cell cannot use a whole carrot, slice of bread or piece of cheese directly. Digestion solves this size problem by making small nutrients, such as sugars and amino acids, small enough to cross from the intestine into the blood and reach cells.
What happens to an apple?
1. You bite the apple and your teeth make smaller pieces. 2. Saliva wets the pieces as you chew and swallow. 3. The stomach mixes them into a soft paste. 4. In the small intestine, useful sugars, water and other nutrients pass into the blood. 5. The large intestine takes back some water and the leftovers leave the body.
The stomach is not the whole system
Because a stomach can feel full, it is reasonable to think that it does all the work. Actually, the stomach mainly mixes food and starts some chemical changes; most nutrient absorption happens later, in the small intestine. Digestion is a team effort along a long tube.
Digestion outside school
Digestion explains why chewing well can make eating easier and why some foods leave more waste than others. It also helps doctors understand problems such as stomach pain or difficulty absorbing nutrients. Strong pain, repeated vomiting or blood in stools needs an adult and medical advice.
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