Lab 8: Digestive System

1. Lab 8: Digestive System

2. Announcements • Exams • Lab notes will be on reserve in library and on the web

3. Goals of the Digestive System • Extract nutrients from food • Transform nutrients into useful forms Ex- oreo= glucose 3. Absorb nutrients and distribute them where they are needed

4. Functions of the Digestive System • Ingestion: intake of nutrients • Digestion: breakdown of large particles into smaller ones • Absorption: uptake of nutrient molecules • Defecation: elimination of undigested residues

5. Actions of the Digestive System 1. Motility • Breaks up food • Moves food through the GI tract (Peristalsis) • Mixes with digestive enzymes • Secretion • Release of enzymes and hormones for chemical digestion and regulation • Membrane Transport - Absorption of nutrients from the tissues by the blood and lymph for transport

6. Stages of Digestion • Mechanical: physical breakdown of food • Chemical: digestive enzymes hydrolyze food particles to break larger molecules into smaller ones • Some nutrients are absorbed with out digestion • Vitamins, minerals, cholesterol, water

7. Oral Cavity Pharynx Esophagus Stomach Pyloric Sphincter Small Intestine Large Intestine Anatomy of the Digestive System

8. Teeth Tongue Salivary Glands Liver Gall Bladder Pancreas Accessory Organs

9. Functions: A. Ingestion: cheeks lips and tongue mobilize food B. Digestion: Mechanical Mastication Chemical 3 salivary glands Digests some starches and fat Oral Cavity

10. Motility: pharyngeal constrictors force food down during swallowing Pharynx

11. Straight muscular tube about 1 foot long Motility: muscular contraction moves food towards stomach www.mywebmd.ca.com Esophagus

12. Heartburn and the Esophagus Heartburn, “ acid reflux”, is caused by acid and food going from the stomach into the esophagus The diaphragm normally prevents acid reflux, in conjunction with the lower esophageal sphincter. When this fails, the burning sensation felt is known as “heartburn” May be linked to a rare type of cancer, adenocarcinoma

13. Muscular sac on the left side of the peritoneal cavity Functions: Food storage Mechanical digestion Chemical digestion Stomach

14. Rugae- folds in the stomach lining that allow it to expand with more food How do we vomit? http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion Rugae in the Stomach

15. Ring of smooth muscle Regulates the passage of material from the stomach into the duodenum http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion Pyloric Sphincter

16. Digestion in the Stomach • Mechanical Digestion: • Muscular contraction • Chemical Digestion: • Secretes digestive enzymes and HCl

17. http://www.afns.ualberta.ca/bbo/1/ANATOMY/SI1.asp 2 meters long, 1 inch in diameter, 5-6 meters in cadaver Functions: Chemical Digestion Nutrient Absorption Motility Small Intestine

18. Duodenum (25 cm): Receives stomach contents, pancreatic juice and bile Neutralizes stomach acid and pepsin Pancreatic enzymes and bile take over chemical digestion Fig 25.22 Anatomy of the Small Intestine

19. Jejunum (2.5m) Ileum (3.6 m) Reabsorbs bile acids Anatomy of the Small Intestine

20. Motility: smooth muscle contract Digestion: chemical enzymes received from the pancreas, liver and gall bladder Nutrient reabsorption: microvilli increase surface area Functions of the Small Intestine Microvilli

21. Dynamic Human: Microvilli

22. Large Intestine • Functions • Motility • Reabsorbtion of Water and Electrolytes • Symbiotic bacteria • Synthesis Vitamins B & K

23. Transverse Colon: right to left Ascending Colon: Descending Colon: up the right side down the left side Cecum: sac on Sigmoid Colon: lower right side S-shaped Anatomy of the Large Intestine

24. Rectum: straight down Anal Canal: out the body Appendix: hangs off cecum Important in Immunity Anatomy of the Large Intestine

25. Enzymes Involved in Chemical Digestion • Saliva: • Amylase: breaks down starch • Lipase: breaks down fats when it enters the stomach • Low pH of the stomach activates the enzyme

26. Enzymes Involved in Chemical Digestion • Stomach: • Digestive chemicals- • HCL: activates enzymes, breaks up foods • Pepsin: digests proteins • Renin: digests milk

27. Pepsin Formation • Interactions between Cells • Chief Cells make pepsinogen • Parietal Cells make HCl • Pepsinogen is cleaved by HCl into Pepsin

28. Dynamic Human: Pepsin Formation

29. Small Intestine Two sources of enzymes Liver and Gall bladder Pancreas Enzymes Involved in Chemical Digestion

30. Enzymes Involved in Chemical Digestion in the Small Intestine • Liver secretes bile that is active in the small intestine • Bile: aids in fat digestion and absorption • Activates pancreatic enzymes • Synthesized from cholesterol • Bacteria in the small intestine use bilirubin to make your feces brown • Gall bladder stores and concentrates bile

31. Gall Stones • What is a gall stone? • How do they treat gall stones? • How is the gall bladder removed?

32. Enzymes Involved in Chemical Digestion in the Small Intestine • Pancreas: secretes pancreatic juice • Amylase: breaks down starch • Lipase: breaks down fats • Ribonuclease (RNAase): breaks down RNA • Deoxyribonuclease (DNAase): breaks down DNA • Zymogens: inactive enzymes that activate in the small intestine

33. Mechanism of Absorption • Membrane Transport: • Nutrients pass through membrane surface • The greater the membrane surface area, the greater the amount of nutrients that can be transported • Surface Area • Rugae • Microvilli

34. Final Destinations of Digestion Products • Starches  bloodstream • Fats  lymph vessels (lacteals) • Proteins  bloodstream

35. Dynamic Human: Visualization

36. Be able to locate and identify Esophagus Stomach Small Intestine Large Intestine Ascending colon Transverse colon Descending colon Also know accessory organs Tongue Teeth Gall Bladder Liver Cat Dissection

37. Conclusion • Review today’s material • Dynamic Human Overview • Know cat anatomy • Lab Practical II returned – well done! • Next week – Endocrine!!!