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Digestive System

Dive into the complexities of the human digestive system, focusing on the stomach and small intestine. This guide covers the structure and function of these organs, the role of gastric juice and its protective mucosa, and the critical processes of protein digestion through enzymes like pepsin and trypsin. Understand how nutrients are absorbed in the small intestine, emphasizing the importance of surface areas such as villi and microvilli. Explore key concepts like sphincters, bile production, and the impact of bacteria on digestive health.

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Digestive System

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  1. Digestive System Part 2 Page 412-417 Practice problems page 420, #1,2,3,4a,5,7,8

  2. Human digestive system

  3. The Stomach • Muscular sac of acid • Performs mechanical and chemical digestion • Starts the breakdown of proteins

  4. The Stomach • Sphincter: • Know the sphincters of the stomach!

  5. The Stomach • Layer to know: Muscularis • Chyme

  6. The Stomach • Mucosa: another layer to know • What is the function of the mucosa • Gastric juice: what is it and how does the mucosa protect itself from it?

  7. Pepsin • Catalyzes the breakdown of proteins into their amino acid subunits • Originally produced as pepsinogen • Page 411, #5

  8. Mucosa • Due to proximity to strong acid, must be constantly regenerated • Ulcer: • Heliobacter pylori: What role does this bacteri play in the production of ulcers?

  9. Human digestive system

  10. Small Intestine • Long (up to 7m), thin (2.5cm) tube • Site of the majority of digestion and absorption

  11. Small Intestine

  12. Small Intestine • Know these and what goes on at each! • Duodenum • Jejunum • Ileum

  13. Small Intestine • Pyloric sphincter:

  14. Pancreas • Bicarbonate ions (HCO3-) • Amylase: • Trypsinogen: • Trypsin: • Compare and contrast pepsin/pepsinogen with trypsin/trypsinogen.

  15. Pancreas • Carboxypeptidase and erepsin: • Lipases: • What difficulty do lipases encounter when digesting food?

  16. Liver • Produces bile • Stores it in the gall bladder • Bile emulsifies fats • What is this and why?

  17. Absorption • Once food is broken down into the smallest subunits, it is absorbed by the cells lining the small intestine and passed into the bloodstream • Occurs in the villi and microvilli

  18. Absorption – Surface area

  19. Absorption – Surface area • Ridges • Villi • Epithelial cells • Microvilli

  20. Absorption – Surface area

  21. Absorption - Transport • How do nutrients get absorbed? • Passive transport: • Diffusion • Osmosis • Facilitated diffusion • Know examples of molecules that get transported by these mechanisms!

  22. Absorption – Passive Transport

  23. Absorption – Active transport • Active transport: • Involves movement of molecules against a concentration gradient

  24. Absorption – Passive Transport

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