Chapter 17: The Digestive System

1. VERY Basic Chapter 17: The Digestive System

2. But first… A video • http://www.youtube.com/watch?v=bfOyLuknD_4

3. Alimentary Canal • Extends from the mouth to the anus • Mouth • Pharynx • Esophagus • Stomach • Small and large intestine • Rectum • Anus • Accessory organs • Salivary glands • Liver • Gall bladder • Pancreas

4. Layers of the Wall • Mucosa (mucous membrane) • Epithelium, connective tissue and smooth muscle • Secretion and absorption • Submucosa • Loose connective tissue, blood vessels, lymphatic vessels, nerves • Nourishment, transport absorbed materials • Muscular layer • Smooth muscle in circular and longitudinal groups • Movement of the tube and its contents • Serosa • Epithelium, connective tissue • Protection

5. Movements of the Alimentary Canal • Mixing • Segmentation • Peristalsis

6. Mouth • Site of both mechanical and chemical digestion • Teeth and chewing (mastication)

7. Mouth • Tongue: root, body • Lingual frenulum • Uvula – extension of soft palate • Division between the pharynx and the nasal cavity • Tonsils (lymphatic tissue) • Palatine • Lingual • Pharyngeal

8. Teeth • Incisor • Canine • Premolar • Molar • Adult has 32 teeth (permanent) • Children have 20 teeth (deciduous)

9. Pharynx and Esophagus • Neither are involved in digestion • Epiglottis

10. Pharynx • Connects the nasal and oral cavities with the larynx and esophagus • Skeletal muscles control swallowing • Under voluntary control

11. Swallowing • 3 stages: • Food is chewed and mixed with saliva • Formation of a bolus • Food is pushed to the pharynx to enter the esophagus • Triggers a swallowing reflex • Peristalsis transports food from esophagus to stomach

12. Esophagus • Connects mouth to stomach • Lined with mucous glands • Cardiac sphincter (Lower esophageal sphincter)

13. Recap • Food enters the mouth…then what? • What types of digestion takes place? • What organs/structures are involved? • Is it voluntary or involuntary?

14. Stomach • Receives food from the esophagus • Digestion • Muscle fibers run in all directions • Circular • Longitudinal • Oblique • Very minimal absorption

15. Stomach • Inner lining: rugae – thick folds • Greater curvature • Lesser curvature • Regions of the stomach: • Cardia • Fundus • Body • Pylorus • Pyloric sphincter

16. Stomach • As the food is digested, it changes from a bolus (from the mouth and esophagus) to chyme • Chyme • Semifluid paste • Food mixed with digestive enzymes

18. Accessory Organs • Pancreas • Liver • Gall Bladder

19. Pancreas • Secretion of pancreas juice • Aids in digestion of • Carbohydrates • Fats • Protein • Nucleic acid

20. Liver • Multi lobed • Makes bile • Digestion of fats

21. Liver

22. Gall Bladder • Connected to the liver • Storage and release of bile into small intestine

23. Small Intestine • Fills most of the abdominal cavity • 5.5 – 6 meters long • Receives secretions from pancreas, liver • Absorption

24. Small Intestine • Duodenum • Jejunum • Vascular • Thicker wall • Ileum • High number of lymph nodes (Peyer’s patches)

25. Small Intestine • Mesentary • Connective tissue around the small intestine • Greater omentum • Membrane drapes over lower digestive tract • If infection occurs, omentum will seal off portion of digestive system • Prevents spread of infection to abdominal cavity

26. Greater Omentum

27. Small Intestine • Villi • Projections to increase surface area

28. Large Intestine • Joins small intestine at the ileum • Water and electrolyte absorption • Formation of feces

29. Large Intestine • Cecum • Appendix – projection from cecum • Colon: • Ascending • Transverse • Descending • Sigmoid • Rectum • Anus

32. Digestive Enzyme Table

33. Digestive System Dissection