2.3 HUMAN DIGESTIVE SYSTEM

1. 2.3 HUMAN DIGESTIVE SYSTEM

2. Learning outcome •  explain what digestion is. • identify the parts of the digestive system. • describe the flow of food particles in the alimentary canal. • state the functions of the organs in the digestive system. • describe the process of digestion in the alimentary canal. • list the end products of digestion of carbohydrate, protein and fats.

3. Digestion • Process of breaking down complex food to simple molecule for absorption into the blood circulatory system.

4. 2 stages: • Physical digestion – big pieces of food are broken down into smaller pieces by teeth • Chemical digestion – enzymes break up complex food molecules into smaller molecules.

5. Enzyme • What is enzyme???? • Protein that speed up the process of digestion. • Characteristic of enzymes • required in small quantities • Not destroyed at the end of digestion • Act only specific foods • Function best at normal body temperature (37 celcius). It destroyed at high temperature. • Specific enzyme act only in specific acidic or alkaline conditions.

6. Digestive system • What must you know???? • Organ that involve in digestive system.. • Mouth, oesophagus, stomach, pancreas, bile duct, gall bladder, liver, small intestine, large intestine, large intestine, anus • Alimentary canal start from mouth, oesophagus, stomach, small intestine, large intestine and the end at anus. • Process of peristalsis – food that pushed along the alimentary canal by contract and relax of muscular walls

8. Mouth (physical digestion) • Food chewed and broken up into small pieces by the teeth. • Small pieces of food have wide surface are for the saliva to act upon. • The salivary gland secrets saliva that is alkaline and contains salivary amylase • Salivary amylase convert starch into maltose Salivary amylase Starch maltose

9. Oesophagus • No digestion take place. Why??? • Food from mouth pushed through oesophagus(gullet) into the stomach by the alternating muscular contraction and relaxation of the oesophagus • Process peristalsis.

10. Stomach • Food mixed with gastric juice • What is gastric juice??? • Juice that secreted from the cell at stomach wall. • Contain Hydrochloric acid and enzyme rennin and pepsin

11. Hydrochloric acid • Function of hydrochloric acid • Providing and acidic medium for enzymic action • Killing bacteria found in food • Neutralising the alkaline property of saliva and stopping the action of salivary amylase

12. Cont… • Pepsin • Digest protein into peptones Protein Peptone • Rennin • Coagulates milk in the stomach to help in the enzymic action of pepsin Liquid milk protein Solid milk protein Pepsin Rennin

13. Small intestine • The duodenum is first part of the small intestine • Receive bile and pancreatic juices

14. Bile • Bile produced by liver and stored in the gall bladder. • Bile flows from gall bladder into the duodenum through the bile duct. • Function of bile: • Emulsification of fat • Preparation of an alkaline medium for enzymic action

15. Pancreatic juice • Produced by pancreas cell • Contain 3 type of enzyme • Pancreatic amylase(digest starch) • Starch maltose • Protease( digest peptones) • Peptones amino acods • Lipase • Fat fatty acids+ glycerol Pancreatic amylase Protease lipase

16. Small intestine also produce enzyme maltase that digest maltose into glucose • Digestion is completed in the small intestine • It ready to be absorbed into the blood stream through the thin wall of the small intestine

17. Large intestine • Absorb water • Undigested food is expelled from the body through the anus as faeces

18. End products of digestion • The end product must in simple forms that readily absorbed into the small intestine through villi amylase maltase pepsin protease bile lipase

19. The end