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Overview of the Digestive System

Overview of the Digestive System. Digestive Tract: Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon) Accessory Organs: Teeth, tongue, salivary glands, pancreas, liver, and gallbladder. Components of the Digestive System. GI Tract: Oral Cavity Pharynx

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Overview of the Digestive System

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  1. Overview of the Digestive System Digestive Tract: Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon) Accessory Organs: Teeth, tongue, salivary glands, pancreas, liver, and gallbladder

  2. Components of the Digestive System • GI Tract: • Oral Cavity • Pharynx • Esophagus • Stomach • Small Intestine • Large Intestine

  3. Teeth

  4. Oral Cavity

  5. The Pharynx • Nasopharynx • Oropharynx • Laryngopharynx

  6. Salivary Glands

  7. The Esophagus

  8. Peristalsis in Esophagus LE 21-8 Muscles contract Muscles contract, constricting passageway and pushing bolus down Muscles relax Bolus of food Muscles relax, allowing passageway to open Muscles contract Muscles relax Stomach

  9. Stomach • Site where food is churned into chyme • Protein digestion begins

  10. Stomach

  11. Stomach

  12. LE 21-11a Duodenum and Related Organs Liver Bile Gall- bladder Stomach Bile Pancreas Acid chyme Intestinal enzymes Pancreatic juice Duodenum of small intestine

  13. Duodenum and Related Organs

  14. Small Intestine – Gross Anatomy • Longest portion of the alimentary canal • Site of most enzymatic digestion and absorption • Three subdivisions • Duodenum, jejunum, and ileum

  15. Gross Anatomy of Large Intestine • Cecum • Appendix • Ascending • Transverse • Descending • Sigmoid colon • Rectum • Anus

  16. LE 21-12 Large intestine (colon) Small intestine Sphincter End of small intestine Rectum Anus Nutrient flow Appendix Cecum

  17. Gross Anatomy of Large Intestine • Rectum – descends along the inferior half of the sacrum • Anal Canal – the last subdivision of the large intestine

  18. Pancreas

  19. Gallbladder • Stores and concentrates bile • Expels bile into duodenum • Bile emulsifies fats

  20. Gallbladder

  21. Visceral Surface of the Liver

  22. Histology of the Digestive Tract Mucosa Submucosa Muscularis Externa Serosa

  23. Mucosa (Innermost Layer) • Epithelium • Connective Tissue (Blood vessels, lymphatic vessels, lymphatic nodules) • Smooth Muscle

  24. Submucosa Connective tissue • Blood vessels • Lymphatic vessels • Nerve plexus • May have glands and lymphatic tissue

  25. Muscularis Externa Smooth or Skeletal Muscle If smooth muscle, usually 2 layers (circular and longitudinal)

  26. Adventitia or Serosa Adventitia (organs superior to diaphragm) Serosa = visceral peritoneum

  27. The Esophagus • Stratified squamous epithelium • Mucous glands • Muscularis externa – skeletal muscle first third of length

  28. Stomach – Microscopic Anatomy

  29. Stomach – Microscopic Anatomy

  30. Small Intestine: Peyer’s Patches

  31. The Stomach – Microscopic Anatomy

  32. The Small Intestine – Structural Features

  33. Small Intestine – Microscopic Anatomy

  34. LE 21-11b Lumen of intestine Nutrient absorption Vein with blood en route to the liver Nutrient absorption into epithelial cells Microvilli Epithelial cells Amino acids and sugars Fatty acids and glycerol Lumen Muscle layers Fats Blood capillaries Large circular folds Blood Villi Lymph vessel Lymph Nutrient absorption Epithelial cells Villi Intestinal wall

  35. Small Intestine: Duodenum Br = Brunner glands V = Villus G = Goblet cells Cr = Intestinal glands MM = Muscularis Mucosae LP = Lamina Propria

  36. Microscopic Anatomy of Large Intestine • Villi are absent • Contains numerous goblet cells • Intestinal crypts – simple tubular glands • Lined with simple columnar epithelial tissue • Epithelium changes at anal canal • Becomes stratified squamous epithelium

  37. Microscopic Anatomy of Large Intestine

  38. Liver • Largest gland in the body • Performs over 500 functions • Digestive function – bile production • Performs many metabolic functions

  39. Microscopic Anatomy of Liver

  40. Microscopic Anatomy of Liver

  41. The Peritoneal Cavity and Peritoneum • Mesentery – a double layer of peritoneum • Holds organs in place • Sites of fat storage • Provides a route for circulatory vessels and nerves

  42. Mesenteries • Superficial view of the abdominal organs

  43. Mesenteries • Greater omentum and transverse colon reflected

  44. Mesenteries • Sagittal section through the abdominopelvic cavity

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