25 Desember 2009

The Digestive System

Rectangular Callout: IdentificationWhen we’re hungry and we smell dinner, our mouth produces water. This is the first step in changing the food we eat into the kind of food that cells can use. This change is called digestion, and it begins in the mouth.
Suppose we are eating sandwich. Our front teeth cut and tear the sandwich. The molars grind it, saliva, the juice in the mouth, gets everything moist.
Rectangular Callout: DescriptionSaliva also contains a type of chemical called an enzyme. It starts breaking down the starch of the bread into sugar.
The moist of the food is carried to the back of the mouth by the tongue. Muscles force the food into to esophagus, behind the windpipe. Other muscles force the food to esophagus. They do their work so well that the food would travel along even if the person were doing a headstand.

Tidak ada komentar:

Posting Komentar