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Digestive System

Digestive System. I. General Description and Considerations. A. Paradox of similarity and change. All organs of the GI tract are modifications of a simple tube Epithelium of the entire tract is derived from a single embryonic germ cell layer

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Digestive System

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  1. Digestive System I. General Description and Considerations

  2. A. Paradox of similarity and change • All organs of the GI tract are modifications of a simple tube • Epithelium of the entire tract is derived from a single embryonic germ cell layer • All organs have some function related to digestion • All areas of the tract have basically the same histological layers

  3. A. Paradox of similarity and change However, • Abrupt changes occur in the epithelium from one organ to the next • Drastic modifications of the mucosa occur from one organ to the next • Each organ along the tract performs a separate and unique function related to digestion

  4. B. General description • Mucosa • Epithelium • Lamina propria • Muscularis mucosa • Submucosa • Muscularis externa • Adventitia

  5. General Plan of the GI Tract

  6. Digestive System II. Esophagus

  7. A. General description and functions • Length, location, & relationships • Innervation • Functions

  8. II. Esophagus • General • Mucosa • Submucosa • Muscularis • Adventitia

  9. B. Mucosa • Non-keratinized stratified squamous epithelium • Lamina propria • Muscularis mucosa

  10. C. Submucosa • Contributes to large longitudinal folds of esophagus - these smooth out during swallowing

  11. C. Submucosa 2. Contains esophageal glands - compound tubuloalveolar, mucus secreting

  12. D. Muscularis externa • Upper one-third • Middle one-third • Lower one-third • Innervation

  13. E. Adventitia • Intrathoracic portion blends with surrounding dense irregular FECT • Below diaphragm covered with visceral peritoneum

  14. Gastro-Esophageal Junction

  15. Gastro-Esophageal Junction

  16. Gastro-Esophageal Junction

  17. Esophageal Ulcer

  18. Digestive System III. Stomach

  19. A. General description & functions • Role in digestion and storage • 4 gross anatomic vs. 3 histological divisions • Rugae

  20. Stomach Regions & Glands

  21. B. Mucosa • Surface • esophageal-gastric junction - abrupt change from stratified squamous to simple columnar • gastric pits - fine furrows, lead into glands • simple columnar epithelium - forms sheet gland, all mucus secreting, mucus has a basic pH

  22. Gastric Lining Cells & Pits

  23. B. Mucosa • Gastric gland structure & nomenclature • simple, branched tubular glands - occupy entire thickness of mucosa • each gland has a neck, body, and base

  24. B. Mucosa • Gastric gland structure & nomenclature • simple, branched tubular glands - occupy entire thickness of mucosa • each gland has a neck, body, and base

  25. B. Mucosa • Lamina propria • occupies space between glands and pits • richly vascularized and slips of smooth muscle from muscularis mucosa

  26. B. Mucosa • Cardiac glands • in cardiac region of stomach, near esophageal orifice • length of gland approximately equal to depth of pit • mostly mucus secreting cells with a few parietal and enteroendocrine cells • primary function is to produce a protective mucus secretion

  27. B. Mucosa • Cardiac glands

  28. B. Mucosa • Fundic glands • located in fundic and body regions of stomach • one or more open into each gastric pit, glands are much longer than their pits are deep • classified as simple branched tubular • closely packed, perpendicular to surface • major source of gastric juice

  29. B. Mucosa • Fundic glands

  30. B. Mucosa • Fundic gland cells • Mucus Neck • Parietal • Chief • Enteroendocrine

  31. Fundic Stomach

  32. Gastric Pits

  33. Fundic Glands – Neck & Body

  34. Parietal Cell

  35. Fundic Glands - Base

  36. Enteroendocrine Cells

  37. Enteroendocrine Cell

  38. B. Mucosa 7. Pyloric glands

  39. Pyloric Stomach

  40. Meisner’s Plexus

  41. Muscularis Externa

  42. Auerbach’s Plexus

  43. Gastric Ulcer

  44. Gastroduodenal Junction

  45. Gastroduodenal Junction

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