SNC4M The Digestive System

1. SNC4M The Digestive System

3. Sound familiar? • Watch this!

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

5. Your task…should you accept it… • Read the section “The Digestive System” starting on page 183 • Make a chart and fill it in as you go along:

6. Organs to Include • Mouth • Tongue • Esophagus • Stomach • Small intestine • Large intestine • Rectum • Anus • Liver • Gall bladder • Pancreas

7. 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

8. 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

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

10. 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

11. 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.

12. 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

13. Has this ever happened to you? • http://www.youtube.com/watch?v=naLJFb9r2ag

14. Cows have how many stomachs? • Cows do not have 4 stomachs; they have one stomach with 4 digestive compartments • They rely on micro-organisms (a large amount) to help digest cellulose (which comes from nutrient-poor grass)

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

16. SMALL INTESTINE • 1st section - duodenum - majority of digestion • 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

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

18. Regions of the Small Intestine Figure 24.16a

19. The Intestinal Wall Figure 24.17b, c

20. 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

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

22. 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.

23. 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

24. 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)

25. 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

26. Figure 24.21 The Gallbladder Figure 24.21a, b

27. HOME 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

28. Peristalsis

29. Peristalsis (contd.)

30. Peristalsis (contd.)

31. Intestinal Bacteria – good? • Scientists estimate that a healthy woman’s body is inhabited by 750 trillion bacteria, yeast, and other microorganisms, mostly colonizing the GI tract • ~3-5 lbs. of your total body weight! • We’ve evolved a mutually beneficial, symbiotic relationship with some bacteria

32. Beneficial Bacteria • Many species manufacture B vitamins and vitamin K and help digest foods • Good intestinal bacteria helps prevent bloating, gas, and yeast overgrowth by controlling the pH level, or acidity, of the intestines • Fermented foods such as miso, tempeh, soy sauce, and yogurt introduce active probiotic cultures that help wedge out unfriendly bacteria

33. Digestion in Action! • Video 1

34. How long does it take? • Digestion time varies depending on the individual • For healthy adults, it's usually between 24 and 72 hours • After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine • Elimination of undigested food residue through the large intestine usually begins after 24 hours

35. Homework • Answer questions #1-2, 4-7, 10 (skip over the chemicals/enzymes we haven’t covered)