Isaac Han (8) Koh Huai Ze (10) Liu Shuyang (14) Ng Wei Kai (16)

1. The Digestive System Isaac Han (8) Koh Huai Ze (10) Liu Shuyang (14) Ng Wei Kai (16)

2. Digestion – A brief introduction The breakdown of food into smaller pieces to allow easy absorption into the blood stream • Lipids are broken down into fatty acids • Proteins are broken down into individual amino acids • Carbohydrates are broken down into simple sugars

3. Digestion – Why it is Important? • Foods that we eat must be broken down into smaller pieces before they can be absorbed into the blood and carried to cells throughout the body. • Our body requires these foods to build and nourish cells and to provide energy through respiration.

4. The Digestive System The digestive system consists of: • The digestive tract A series of hollow organs joined in a long, twisting tube from the mouth to the anus • Other organs that help the body break down and absorb food Liver Pancreas

5. The Digestive Tract • Consists of: • Mouth • Esophagus • Stomach • Small Intestine • Large Intestine • (Colon) • Rectum • Anus Hollow organs

6. The Digestive Tract • These hollow organs contain a lining called the mucosa • In the mouth, stomach and small intestine, the mucosa contains tiny glands that produce digestive juices to help digest food • The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract

7. Other organs • Liver, pancreas and gallbladder “solid” digestive organs • The liver and pancreas produce digestive juices that reach the intestine through small tubes called ducts • The gallbladder stores the liver’s digestive juices until they are needed in the intestine

8. How is food digested? • Digestion involves making food with digestive juices, moving it through the digestive tract, and breaking it down into smaller molecules • It begins in the mouth, and is completed in the small intestine

9. Mouth • Beginning of the digestive system • Chews up food into smaller pieces to aid digestion • Lined with a mucous membrane • Produces saliva which breaks down some starch and fats in the food

10. Esophagus Esophagus • Swallowed food is pushed into the esophagus • Connects the mouth with the stomach below Lower esophageal sphincter • Ring-like muscle • Located at the junction of the esophagus and stomach • In charge of closing the passage between the two organs • As food approaches it, it relaxes and allows the food to pass through to the stomach

11. Stomach Functions: • Stores the swallowed food and liquid – muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material • Through a churning action, mixes the food and liquid with digestive juices produced by the stomach to digest them • Empty its contents slowly into the small intestine Carbohydrates spend the least amount of time in the stomach, while proteins stay in the stomach longer, and fats the longest.

12. Small Intestine • Much of the digestion and absorption of food takes place here • Primary function: to absorbnutrients and minerals found in food • The mucosa of the small intestine contains many folds called villi • The villi are covered with microscopic projections called microvilli • The structures create a vast surface area for nutrients to be absorbed

13. Large Intestine • Absorbs water from the remaining indigestible food matter • Connects the small intestine to the rectum • Pass useless waste material from the body • About 1.5m long

14. Rectum • Receives waste matter from the large intestine • When gas or stool comes into the rectum, sensors will send a message to the brain • Act as a temporary storage site for waste matter before it is excreted from the body through the anus • Made up of muscular walls that are able to expand to hold waste material

15. Anus • Disposes waste products out of the body

16. Pancreas • Produces a digestive juice that contains a wide array of enzymes* to break down the carbohydrate, protein and fat in food • Stores bile from the liver *enzymes: substances that speed up chemical reactions in the body

17. Liver • Produces a digestive juice called bile • Bile is stored between meals in the gallbladder • At mealtime, it is squeezed out of the gallbladder into the intestine to mix with the fat in food to dissolve the fats and digest the dissolved fats.