6. The Digestive System
Grade 11 Biology

7. Table of Contents Introduction to the Digestive System
What is Digestion?
2 Phases of Digestion
4 Components of Digestion
The Organs of Digestion

8. Introduction to the Digestive System
The digestive system is an organ system that ingests food, breaks it down into smaller chemical units, and absorbs the nutrient molecules.

9. What is Digestion?
Digestion is the mechanical and chemical breakdown of food into molecules small enough for the body to absorb.

10. 2 Phases of Digestion
Physical Digestion – begins in the mouth where the food is chewed
Chemical Digestion – occurs in the mouth and the stomach

11. 4 Components of Digestion
Ingestion – the intake of nutrients
Digestion – the breakdown of organic molecules
Absorption – the transport of digested nutrients to body tissues
Egestion – the removal of materials from food that the body cannot digest

12. The Organs of
Digestion

13. Mouth Physical digestion begins
Food is chewed into a bolus and mixed with saliva
Initial carbohydrate digestion

14. Esophagus
Peristaltic contractions move the food from the mouth to the stomach through the esophagus.

15. Stomach
Food storage
Initial protein digestion

16. Small Intestine Site of the majority of digestion and absorption
Digestion of proteins, carbohydrates, and lipids
Villi increase surface area of small intestine for absorption

17. Pancreas
Releases enzymes into the small intestine to aid in digestion

18. Liver Produces bile salts which emulsify fats
Storehouse for glycogen and vitamins
Detoxifies many substances in the body

19. Gall Bladder
Stores bile salts

20. Large Intestine Stores food wastes long enough to reabsorb water
Houses bacteria which use waste materials to synthesize vitamins

21. Credits Nelson Biology, Bob Ritter, Nelson Canada, 1993.