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The Digestive System and Body Metabolism Ch 14b

The Digestive System and Body Metabolism Ch 14b. Stomach Anatomy. Located on the left side of the abdominal cavity C shaped Hidden by liver and diaphragm Food enters at the cardioesophageal sphincter Sphincter = valve. Stomach Anatomy. Regions of the stomach

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The Digestive System and Body Metabolism Ch 14b

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  1. The Digestive System and Body MetabolismCh 14b

  2. Stomach Anatomy • Located on the left side of the abdominal cavity • C shaped • Hidden by liver and diaphragm • Food enters at the cardioesophageal sphincter • Sphincter = valve

  3. Stomach Anatomy • Regions of the stomach • Cardiac region – near the heart • Surrounds cardioesophageal sphincter – where food goes from esophagus to stomach • Fundus – expanded part • Lateral to cardiac region • Body – midportion • Narrows into pyloric antrum & then pylorus (terminal end) • Pylorus – funnel-shaped terminal end • Food empties into the small intestine at the pyloric sphincter

  4. Stomach

  5. Stomach Anatomy • 25 cm long = 10” • Can hold up to 4L = 1 gallon • Rugae – internal folds of the mucosa • External regions • Lesser curvature – concave medial surface • Greater curvature – convex lateral surface

  6. Stomach Anatomy • Layers of peritoneum attached to the stomach • Lesser omentum – attaches the liver to the lesser curvature • Greater omentum – attaches the greater curvature to the posterior body wall • Contains fat to insulate, cushion, and protect abdominal organs • Contains lymph nodules

  7. Stomach Anatomy Figure 14.4a

  8. Stomach Functions • Acts as a storage tank for food • Site of food breakdown - churns • Chemical breakdown of protein begins • Delivers chyme (processed food) to the small intestine - creamy • 3 muscle layers • Muscularis externa – longitudinal, outside • Circular – middle • Oblique- inner

  9. Specialized Mucosa of the Stomach • Simple columnar epithelium • Mucous neck cells – produce a sticky alkaline mucus • To protect stomach from acid • Gastric glands – secrete gastric juice • Chief cells – produce protein-digesting enzymes (pepsinogens) • Parietal cells – produce hydrochloric acid • Endocrine cells – produce gastrin

  10. Niagra Falls

  11. Some cells produce intrinsic factor • Needed for absorption of vitamin B12 in small intestine • Most digestion in pyloric region

  12. Layers of stomach

  13. Structure of the Stomach Mucosa • Gastric pits formed by folded mucosa • Glands and specialized cells are in the gastric gland region

  14. Structure of the Stomach Mucosa Figure 14.4b–c

  15. Small Intestine • 2.5-7m = 8-18’ • The body’s major digestive organ • Site of nutrient absorption into the blood • Muscular tube extending form the pyloric sphincter to the ileocecal valve • Suspended from the posterior abdominal wall by the mesentery

  16. Subdivisions of the Small Intestine • Duodenum (5% of total length) • Attached to the stomach • Curves around the head of the pancreas • Jejunum (37%) • Attaches anteriorly to the duodenum • Ileum (58%) • Extends from jejunum to large intestine

  17. Chemical Digestion in the Small Intestine • Pyloric sphincter controls amount of food from stomach to small intestine • Source of enzymes that are mixed with chyme • Intestinal cells • Pancreas – through pancreatic duct • Bile enters from the gall bladder (originally from liver) • Hepatopancreatic ampulla – pancreatic & bile ducts join • All food absorption occurs in small intestine

  18. Chemical Digestion in the Small Intestine Figure 14.6

  19. Niagra Falls

  20. Villi of the Small Intestine • Fingerlike structures formed by the mucosa • Give the small intestine more surface area Figure 14.7a

  21. Villi of small intestine

  22. Microvilli of the Small Intestine • Small projections of the plasma membrane • Found on absorptive cells Figure 14.7c

  23. Model of small intestine

  24. Structures Involved in Absorptionof Nutrients • Absorptive cells • Blood capillaries • Lacteals (specialized lymphatic capillaries) Figure 14.7b

  25. Folds of the Small Intestine • Called circular folds or plicae circulares • Deep folds of the mucosa and submucosa • Do not disappear when filled with food • The submucosa has Peyer’s patches (collections of lymphatic tissue – to help deal with bacteria)

  26. Large Intestine • Larger in diameter, but shorter than the small intestine • 5’ • Frames the internal abdomen

  27. Niagra Falls in winter

  28. Large Intestine Figure 14.8

  29. Functions of the Large Intestine • Absorption of water • Eliminates indigestible food from the body as feces • Does not participate in digestion of food • Goblet cells produce mucus to act as a lubricant • No villi

  30. Structures of the Large Intestine • Cecum – saclike first part of the large intestine • Appendix • Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) • Hangs from the cecum

  31. Structures of the Large Intestine • Colon • Ascending • Transverse • Descending • S-shaped sigmoidal • Rectum • Anus – external body opening • Sigmoid, rectum and anus are in pelvic cavity

  32. Modifications to the Muscularis Externa in the Large Intestine • Smooth muscle is reduced to three bands (teniae coli) • Muscle bands have some degree of tone • Walls are formed into pocketlike sacs called haustra

  33. Accessory Digestive Organs • Salivary glands • Teeth • Pancreas • Liver • Gall bladder

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