Objective: You will be able to identify the structures of the digestive system.

1. Objective:You will be able to identify the structures of the digestive system. Do Now: • Read all of page 978 • Give the function of the digestive system

2. Smallmolecules Piecesof food Chemical digestion(enzymatic hydrolysis) Nutrient moleculesenter body cells Mechanicaldigestion Undigested material Food ELIMINATION ABSORPTION DIGESTION INGESTION 1 2 4 3 Figure 41.12 The four stages of food processing

3. Figure 41.13 The human digestive system

4. Oral Cavity • Mechanical digestion breaks food into smaller pieces • Increases surface area for chemical digestion • Chemical digestion of starch occurs here • Done by salivary amylase

5. Esophagus • No digestion occurs here • It moves food from oral cavity to stomach by using muscles • Called peristalsis

6. Bolus of food Tongue Epiglottisup Pharynx Esophageal sphinctercontracted Glottis Larynx Trachea Esophagus To lungs To stomach Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 1)

7. Bolus of food Tongue Epiglottisup Pharynx Esophageal sphincterrelaxed Glottis Esophageal sphinctercontracted Epiglottis down Larynx Trachea Esophagus To lungs To stomach Glottis upand closed Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 2)

8. Epiglottisup Bolus of food Tongue Glottisdown and open Epiglottisup Pharynx Esophageal sphincterrelaxed Esophageal sphinctercontracted Esophageal sphinctercontracted Glottis Epiglottis down Larynx Trachea Esophagus To lungs To stomach Glottis upand closed Contractedmuscles Relaxedmuscles Relaxedmuscles Figure 41.16 From mouth to stomach: the swallowing reflex and esophageal peristalsis (layer 3)

9. Esophagus Cardiac orifice Stomach Pyloric sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface of stomach. The interior surface of the stomach wall is highly folded and dotted with pit leading into tubular gastric glands. Epithelium Pepsinogen Pepsin (active enzyme) 3 3 1 1 2 2 Gastric gland. The gastric glands have three types of cells that secrete different components of the gastric juice: mucus cells, chief cells, and parietal cells. HCl Pepsinogen and HCI are secreted into the lumen of the stomach. HCl converts pepsinogen to pepsin. Mucus cells secrete mucus, which lubricates and protects the cells lining the stomach. Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. Chief cells secrete pepsino- gen, an inactive form of the digestive enzyme pepsin. Parietal cell Chief cell Parietal cells secrete hydrochloric acid (HCl).

10. Stomach • Mechanical digestion occurs by the grinding of the stomach’s muscles • Chemical digestion of proteins begins here • Gastric glands in stomach release a HCl and protease • The HCl provides a highly acidic environment • The protease actually breaks down the protein

11. Liver Bile Gall-bladder Stomach Acid chyme Intestinaljuice Pancreatic juice Pancreas Duodenum of small intestine Figure 41.19 The duodenum

12. Small Intestine • Lipid digestion starts here • Most of the chemical digestion occurs here • Intestinal glands and the accessory organs help to digest food • Liver, gall bladder and pancreas • All of the absorption of food into the body occurs here • No food is digested AFTER it leaves the small intestine

13. Liver Bile Gall-bladder Stomach Acid chyme Intestinaljuice Pancreatic juice Pancreas Duodenum of small intestine Figure 41.19 The duodenum

14. Accessory organs • The liver makes the bile but it stores it in the gall bladder • It’s the gall bladder that actually secretes bile into the small intestine • Bile emulsifies fats (breaks them down) • The pancreas secretes amylase, protease and lipase

15. Liver Bile Gall-bladder Stomach Acid chyme Intestinaljuice Pancreatic juice Pancreas Duodenum of small intestine Figure 41.19 The duodenum

16. Large Intestine • This organs main function is to absorb water • It does NOT absorb food nor does it digest food!!!!

17. End of the line • Strong peristaltic action from the rectum pushes waste out of the anus

18. Group Roles • Leader – keeps the group focused and on task • Recorder – Writes down the work for the group • Reporter – Informs the class/teacher about the work done by the group • Noise monitor – Makes sure that the group works quietly

19. Activity • Create story about the digestive canal of horrors where a group of teenage worm friends enter a tunnel but end up being digested by enzymes • Remember that only some of the carbohydrate and protein digestion happens outside intestines • Be sure to include each structure and describe in full detail what they do.

20. Objective:You will be able list and describe the disorders that affect the digestive system. Do Now: • Read “Absorption in the small intestine” on p. 982-983 • Describe the structure of the villi

21. Muscle layers Figure 41.23 The structure of the small intestine Microvilli(brush border) Vein carrying blood to hepatic portal vessel Bloodcapillaries Epithelialcells Epithelial cells Largecircularfolds Lacteal Villi Key Lymph vessel Villi Nutrientabsorption Intestinal wall

22. Bacteria Mucuslayer of stomach 1 µm Figure 41.18 Ulcer-causing bacteria

23. Disorders of the Digestive System • Ulcers are erosions of the digestive tract • Appendicitis is the infection and inflammation of the appendix • Gallstones is the accumulation of hardened cholesterol deposits on the gall bladder

24. Disorders continued • Constipation occurs when the large intestine absorbs too much water • Diarrhea occurs when the large intestine does NOT absorb enough water

25. Objective:You will be able to answer review questions on the digestive system. Do Now: • Read all of page 971 • Besides energy, what are the other uses of food?