Identify that humans are consumers and must eat and digest food. Identify and explain the roles of the organs of the digestive system. Explore the health of the human digestive system.
We need food for energy and growth. The food we eat is too big to be delivered directly to the cells of our bodies.
Our digestive system breaks down food into smaller molecules. After the food is digested it can pass into our blood. The blood then carries the food molecules to our cells.
There are two types of digestion:
1. Physical digestion: food is broken down into smaller pieces by the teeth, tongue and churning action of the muscles in the stomach.
z Fig. 8.2.1
The stages of human nutrition
2. Chemical digestion: food is broken down into simpler molecules by digestive enzymes and other digestive juices, including acid, in the stomach.
The Stages in Nutrition There are five stages of human nutrition:
Ingestion
1. Ingestion: the food is taken into the mouth.
2. Digestion: the food is broken down into simpler, absorbable molecules.
Digestion
3. Absorption: the absorbable molecules are passed into the blood and carried to all of the cells of the body.
Absorption Assimilation
4. Assimilation: the food is used by the body for energy and to build new cells.
5. Egestion: undigested food material is released from the digestive system as faeces.
Egestion and excretion Egestion
Egestion is the release of undigested food. Excretion is the removal of the waste products of chemical reactions that were produced within the cells of the body. The excretory organs include the kidneys, lungs and skin. For example, carbon dioxide produced by respiring cells is excreted via the lungs.
