The Digestive System

1. The Digestive System VIDEO

2. Food Processing • Ingestion – eating or drinking • Digestion – break down molecules to absorb • Hydrolysis: the process of breaking bonds in food molecules by adding water to them in the presence of specific enzymes • Absorption – small intestine • Elimination – removal of wastes

3. What is digestion? • Chemical and mechanical breakdown of organic molecules into units small enough for the body to absorb • These molecules provide: • Energy resources • Raw materials to build materials for the cell

4. 1 2 3 4 THE MOUTH • Physical digestion – chewing and teeth break food into smaller pieces • Saliva moistens food (produced by salivary glands) • Chemical digestion of starch by enzyme amylase, which is dissolved in saliva Canines - Used for tearing Molars – Used for crushing Pre-molars – Used for grinding Incisors – Used for cutting

5. THE TONGUE • Has taste buds that are groups of cells located on the tongue that enable one to recognize different tastes • Assists with moving food around mouth while chewing

6. Check this Out! • http://www.youtube.com/watch?v=2Fhc0t_QNhs

7. What is this called? ESOPHAGUS Food going down the esophagus has a new name, bolus. Peristalsis - contraction and relaxation of the smooth muscle down the esophagus moves bolus down to the stomach The cardiac sphincter opens to allow the bolus of food to enter the stomach

8. Peristalsis VIDEO

9. THE STOMACH • Along with HCl (hydrochloric) acid, enzymes, and muscle contractions, the bolus is churned and broken down further into a solution called chyme • Chemical digestion of protein occurs here by the enzyme pepsin The pyloric sphincter, regulates the movement of chyme to the small intestine. VIDEO

10. How does it work? • The pH of your stomach is about 1-2 (facilitates breakdown of protein) • Stomach cells secrete hydrochloric acid (gastric juices) which helps to break down the food and kills pathogens • A layer of mucous secreted by cells lining the stomach protects the stomach from damage

11. SMALL INTESTINE • 3 sections: duodenum, jejunum, ileum • Digestion is completed here • Undigested food (waste) passes on to the large intestine

12. SMALL INTESTINE • 1st section - duodenum - majority of digestion (fats) • 2nd section - jejunum -absorption of nutrients such as carbohydrates and proteins occur here • 3rd section – ileum - longest section; fats and bile salts are absorbed here

13. SMALL INTESTINE • Contains little finger-like projections called villi which increase the surface area • Why is this advantageous?

14. Regions of the Small Intestine Figure 24.16a

15. The Intestinal Wall Figure 24.17b, c

16. THE COLON (LARGE INTESTINE) • Undigested food is not needed by the body • Waste is stored and eliminated • Absorption of water, vitamins, minerals, and inorganic salts • Most of the water from food is reabsorbed here • Bacteria that reside in the colon produce vitamin B12

17. THE RECTUM • “Warehouse for feces” • Waste (feces) is stored here until it is ready to be excreted

18. THE ANUS • Opening at the far end of the digestive tract through where stool leaves the body • A muscular ring (anal sphincter) keeps the anus closed until a person has a bowel movement.

19. The Pancreas • HCl enters the duodenum triggers the production of digestive enzymes • Produces chemicals (bicarbonate) that neutralize stomach acids that pass from the stomach into the small intestine

20. Gallbladder The Liver • The liver produces bile salts which are stored in the Gallbladder • Bile salts aid in the physical breakdown, emulsification, and absorption of fats • Bile is secreted into the small intestine (duodenum)

21. Small Intestine Gallbladder • The bile salts produced by the liver, are stored in the gallbladder • A hormone, CCK, triggers their release into the small intestine

22. Figure 24.21 The Gallbladder Figure 24.21a, b

23. Review Food moves down the esophagus using muscle contractions, called peristalsis. The mouth contains different teeth, used for different purposes. The stomach breaks down the food, and passes it on to the small intestine The liver produces bile salts that break down fats. Bile salts are stored in the gall bladder. The pancreas produces enzymes to digest the food The small intestine has three parts. The majority of digestion, and some absorption happens here. The gall bladder, stores the bile salts, and releases them when CCK is present. The colon absorbs the remaining moisture

24. Common Disorders

25. Ulcer • Stomach lining is broken down and irritated by gastric acid • Peptic Ulcers: Sores found in stomach lining, esophagus or upper small intestine

26. Inflammatory Bowel Disorder • IBD • Intestines become irritated and inflamed • Develop many ulcers causing abdominal pain and diarrhea • Crohn’s and colitis

27. Constipation • Two reasons: • Peristalsis moves feces along too slowly • colon absorbs too much water so feces becomes too compacted • Temporary condition – eat fibre, exercise and drink lots of H2O • Sometimes results from surgery, pregnancy, medication, air travel

28. Diarrhea • Lining of colon irritated (bacterial or viral infection) • Less effective in reclaiming water • Can cause dehydration

29. Nausea and Vomiting • Nausea: feeling associated with urge to vomit • Vomiting: expulsion of stomach contents through esophagus and mouth • Safety mechanism for eliminating toxic or foreign contents • Causes: inner ear, drugs, infections, brain, injury, diseases

30. Please Complete • What happens during hydrolysis? • Compare and contrast the terms “mechanical digestion” and “chemical digestion” • In the mouth b) in the stomach • What is bile? What is its role in digestion? • As the end result of digestion: Carbohydrates are broken down to form ____, which provide your cells with _______. Proteins are broken down to form ____, which provide your cells with _______. Fats are broken down to form ____, which provide your cells with _______. • What is the major function of the large intestine?