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Digestive System

The digestive system, or G-I tract, consists of essential components including the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus, measuring approximately 30 feet in length. Accessory organs such as teeth, tongue, gall bladder, salivary glands, liver, and pancreas support digestion through the secretion of saliva, bile, and enzymes. The GI process entails ingestion, propulsion, digestion, absorption, and defecation. Understanding the intricate roles of these organs and their interactions is crucial for comprehending overall digestive health.

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Digestive System

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  1. Digestive System

  2. AKA • G-I Tract • Alimentary Canal

  3. Overview • Consists of • Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus • About 30’ in length • Accessory Organs • Teeth, tongue, gall bladder, salivary glands, liver and pancreas • Glands secrete saliva, bile and enzymes

  4. GI System

  5. Process Includes • Ingestion • Mechanical – chewing, churning • Propulsion – swallowing and peristalsis • Chemical – breakdown via enzymes • Absorption – transport of end products into blood • Defecation – elimination as feces

  6. GI Process

  7. Peritoneum and cavity • Parietal peritoneum surrounds cavity, lines body wall • Visceral surrounds organ • Serous membrane allows organs to glide/expand • Retroperitoneal refers to organs in the dorsal region • Peritonitis = inflammation of peritoneum • Perforation = infection

  8. Peritoneum

  9. Regions

  10. Mesentery • Double layer of peritoneum, holds organs in place • Omentums - protection • Lesser = fatty skin, superficial near the stomach • Greater = deeper, made of connective tissue, significant fat • Three layers of fascia – Skin, Fascia, mesentary

  11. Messentery

  12. Messentary

  13. Omentum

  14. Histology • Smooth muscle - peristalsis • Glands with ducts • Nerves, arteries and veins

  15. Histology

  16. MouthPoint of Origin • Oral cavity • Tongue • Soft and hard palate • Uvula • Oropharynx • Epiglottis • Larynx/pharynx • Esophagus

  17. Mouth Anatomy

  18. Mouth Anatomy

  19. Salivary glands • Produce saliva, a mixture of water, ions, mucous, and enzymes • Dissolve food • Wets food to help bind it to become a bolus • Neutralizes acids, helps growth of beneficial bacteria • Intrinsic –in tongue, palate, lips and cheeks • Extrinsic = outside mouth • Parotids • Submandibular • Sublingual

  20. Salivary Glands

  21. Pharynx • Oso • Laryngopharynx • Lined with epithelial cells for protection

  22. Pharynx

  23. Esophagus • Muscular tube • Propels swallowed food to stomach • Passes through diaphragm (esophageal hiatus) into abdomen • Join the stomach at cardiac orifice • Cardiac sphincter prevents reflux or regurgitation of acid

  24. Esophagus

  25. Esophagus

  26. Stomach • Food churned into chyme; a paste • Secretes pepsin – a protein digesting enzyme and HCl • Waters, electrolytes, some drugs absorbed through stomach • Anatomy • Cardiac orifice, fundus, lesser and greater curvature, pylorus • Rugae = numerous longitudinal folds of mucosa which flatten as stomach fills, allows expand

  27. Stomach

  28. Stomach

  29. Small Intestine • Longest part of alimentary canal • Most enzymes involved in small intestine come from pancreas • Three divisions • Duodenum – 5% • Jejunum – 40% • Ileum – almost 50%

  30. Duodenum • Receives digestive enzymes from pancreas • Bile from gall bladder and liver • Almost all nutrients are absorbed in small intestine • Large surface area, great length

  31. Small Intestine

  32. Small Intestine

  33. Gall Bladder • Cystic duct • Bile duct – empties into small cystic duct • Secrete bile for duodenum digestion • Bile – Right and Left hepatic ducts to common cystic duct to Gall bladder for storage • From GB to bile duct to duodenum

  34. Pancreas • Exocrine gland – produces most enzymes for digestion in small intestine • Endocrine function = produce hormones that regulate levels of sugar in the blood • Main pancreatic duct

  35. Gall Bladder and Pancreas

  36. Large Intestine • Most material has been digested by the time it reaches LI • 12-24 hours in large bowel • Little breakdown • Performs some absorption, especially water • Components • Ascending colon • Transverse colon • Descending colon • Sigmoid to rectum and anus

  37. Large Intestine

  38. Cecum and appendix • Cecum is a small sac (blind pouch) • Valve prevents a back up of fecal matter to ileum • Appendix • Lymph tissue neutralizes bacteria • Diverticulosus – a small outward herniation of colon, especially sigmoid • Diverticulitis – infection with leaks into peritoneal cavity may lead to peritonitis

  39. Anal Canal • ANS balance between defecation or not • PNS = increase movement • SNS = decrease • Voluntary control via external sphincter muscles

  40. Anal Canal

  41. Defecation

  42. Liver • Largest gland in the body (1.4 kg – 3 lbs.) • Produces bile • Stored in GB • Emulsifies fats • Involved in metabolism • Diaphramatic and visceral surface • Right and left lobes • Porta hepatis = major vessels and nerves • Right and left hepatic ducts, common bile, common

  43. Liver

  44. Liver

  45. Liver

  46. Study Points • Know the components of GI Tract • Know the peritoneum • Understand smooth muscle control • Know the various ducts and how they connect to specific organs • Understand the role of the stomach v. small intestine v. large intestine

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