Biology
Understanding the roles of the digestive organs
We are learning how to: • Describe the roles of the oesophagus, stomach, intestine and pancreas in digestion. • Explain how the structure of each of the organs is adapted to its function.
Several organs in the body work together to digest food and dispose of waste. Food is churned, mixed, digested with chemicals and squeezed along the digestive system. Each organ has developed to carry out its specific role. What do the organs of the digestive system do?
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Digestion takes place along the digestive system from the mouth to the small intestine. Once digestion by enzymes is complete in the small intestine, the small molecule nutrients pass into the bloodstream and are carried to cells. 1. Name the organ in which digestion by enzymes is completed. 2. List two parts of the digestive system where physical and chemical digestion take place. 3. Food does not pass through the liver. Explain why it is shown as part of the digestive system.
mouth Physical and chemical digestion (by saliva)
oesophagus
small intestine large intestine
FIGURE 1.2.9a: Each of the organs in the digestive system has a specific role to play.
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The stomach breaks down food physically by muscle contraction and chemically by enzymes. The acid conditions kill bacteria and help the enzymes to work.
stomach pancreas
Chemical digestion
Food is swallowed and passes into the oesophagus which carries the food to the stomach.
teeth tongue
Physical and chemical digestion
Food enters the mouth where it is chewed up, rolled into a ball by the tongue and moistened by saliva ready for swallowing.
The small intestine digests the food further using different enzymes and absorbs it into the blood. In the large intestine water is absorbed to make the waste (faeces) more solid.
appendix anus
The faeces are then passed out through the anus.
KS3 Science Book 1: Eating, Drinking and Breathing
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09/12/2013 15:22