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Digestive System

Digestive System. Ex 38. Overview. Alimentary Canal hollow tube from mouth to anus outside of the body covered with mucous membrane Accessory Digestive Organs teeth, tongue, gallbladder, salivary glands, liver, and pancreas. Oral Cavity. Tongue and Teeth. Oral Cavity. Teeth

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Digestive System

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  1. Digestive System Ex 38

  2. Overview • Alimentary Canal • hollow tube from mouth to anus • outside of the body • covered with mucous membrane • Accessory Digestive Organs • teeth, tongue, gallbladder, salivary glands, liver, and pancreas

  3. Oral Cavity • Tongue and Teeth

  4. Oral Cavity • Teeth • incisors, canines, premolars, molars

  5. Oral Cavity • Salivary Glands • secrete saliva • contains enzymes for digestion • contains mucous for formation of the bolus • Parotid Gland • serous • enzymes • Sublingual Gland • mucous • Submandibular Gland • mixed • demilune

  6. Oral Cavity • Salivary Glands • secrete saliva • contains enzymes for digestion • contains mucous for formation of the bolus • Parotid Gland • serous • enzymes • Sublingual Gland • mucous • Submandibular Gland • mixed • demilune

  7. Oral Cavity

  8. Lumen Overview • Serosa • supports, protects, allows viscera to move without friction • epithelium, connective tissue • Muscularis Externa • contractions cause peristalsis • myenteric plexus • outer longitudinal, inner circular • Submucosa • area for nutrition and protection • carries blood vessels, submucosal plexus, lymph nodules • Mucosa • secretes digestive enzymes & mucous, barrier for bacteria, absorption of food • epithelium, lamina propria, muscularis mucousae

  9. Lumen Overview • Serosa • protects, allows viscera to move without friction • epithelium, connective tissue • Muscularis Externa • contractions cause peristalsis • myenteric plexus • outer longitudinal, inner circular • Submucosa • area for nutrition and protection • carries blood vessels, submucosal plexus, lymph nodules • Mucosa • secretes digestive enzymes & mucous, barrier for bacteria, absorption of food • epithelium, lamina propria, muscularis mucousae

  10. Esophagus • Esophagus • transports food bolus from oropharynx to the stomach via peristaltic action • Body of the esophagus • Sphincters • upper esophageal sphincter • lower esophageal sphincter • defects in sphincter tone can cause disease: GERD and Hiatal Hernia

  11. Esophagus • Esophagus • transports food bolus from oropharynx to the stomach via peristaltic action • Body of the esophagus • Sphincters • upper esophageal sphincter • lower esophageal sphincter • defects in sphincter tone can cause disease: GERD and Hiatal Hernia

  12. Esophagus • Lower Esophageal Sphincter • Made up not only of a muscular band but also forces of the surrounding diaphragm contribute to the lower esophageal tone. • Defects in tone can cause disease • GERD • Hiatal hernia

  13. Esophagus • Mucosa • nonkeratinized stratified squamous epithelium • Submucosa • esophageal glands, submucosal plexus, blood vessels • Muscularis Externa • upper 1/3 voluntary striated smooth muscle • middle 1/3 mixed • lower 1/3 involuntary smooth muscle • myenteric plexus • Adventitia • no serosa

  14. Stomach • Responsible for initial digestion of food • mechanical breakdown through contractions of musculature • secretion of enzymes (namely pepsin) • Parts of the Stomach • lesser curvature • lesser omentum • greater curvature • greater omentum • fundus • cardia • body • antrum or pylorus • pyloric sphincter

  15. Stomach • Responsible for initial digestion of food • Parts of the Stomach • lesser curvature • lesser omentum • greater curvature • greater omentum • fundus • cardia • body • antrum or pylorus • pyloric sphincter • angulus • rugae • increases surface area for absorbtion

  16. Stomach • Mucosa • simple columnar epithelium • gastric pits leading to gastric glands • mucous neck cells, parietal cells (HCL), chief cells (pesinogen) • Submucosa • usual glands, submucosal plexus, blood vessels • Muscularis Externa • inner oblique, middle circular, outer longitudinal • myenteric plexus • Serosa

  17. Stomach • Mucosa • simple columnar epithelium • gastric pits leading to gastric glands • mucous neck cells, parietal cells (HCL), chief cells (pesinogen) • Submucosa • usual glands, submucosal plexus, blood vessels • Muscularis Externa • inner oblique, middle circular, outer longitudinal • myenteric plexus • Serosa

  18. Stomach • Mucosa • simple columnar epithelium • gastric pits leading to gastric glands • mucous neck cells, parietal cells (HCL), chief cells (pesinogen) • Submucosa • usual glands, submucosal plexus, blood vessels • Muscularis Externa • inner oblique, middle circular, outer longitudinal • myenteric plexus • Serosa

  19. Gastric Glands • Gastric Pit • mucous neck cell • thick, alkaline mucous • parietal cell • HCl, intrinsic factor • chief cell • pepsinogen, gastric lipase • G cell • gastrin

  20. Intestine Overview • Small Intestine • pyloric sphincter to ileocecal valve • breaks down food so molecules can be absorbed • duodenum • jejunum • ileum • Large Intestine • fluid absorbtion • some vitamin production • cecum • ascending colon • transverse colon • descending colon • sigmoid colon • rectum

  21. Small Intestine • Duodenum • full chemical mixture for food digestion • bile and pancreatic enzymes enter here • major and minor papillae (spincter of Oddi) • mostly retroperitoneal • most absorption occurs here • Bulb • C-Loop

  22. Small Intestine • Duodenum • full chemical mixture for food digestion • bile and pancreatic enzymes enter here • major and minor papillae (spincter of Oddi) • mostly retroperitoneal • most absorption occurs here • Bulb • C-Loop

  23. Small Intestine • Duodenum • full chemical mixture for food digestion • bile and pancreatic enzymes enter here • major and minor papillae (spincter of Oddi) • mostly retroperitoneal • most absorption occurs here • Bulb • C-Loop

  24. Small Intestine • Jejunum • plicae circularis • free of mesenteric fat

  25. Small Intestine • Ileum • no plicae • mesenteric fat partially attached • important for iron absorbtion

  26. Small Intestine • Mucosa • simple columnar epithelium folded into villi • microvilli on luminal cell surface • crypts of Lieberkuhn • Submucosa • duodenal glands (brunner) • Peyer’s Patches (lymphoid tissue in ileum) • Muscularis Externa • inner circular • outer longitudinal • myenteric plexus • Serosa

  27. Small Intestine

  28. Small Intestine • Mucosa • simple columnar epithelium folded into villi • microvilli on luminal cell surface • crypts of Lieberkuhn • Submucosa • duodenal glands (brunner) • Peyer’s Patches (lymphoid tissue in ileum) • Muscularis Externa • inner circular • outer longitudinal • myenteric plexus • Serosa

  29. Small Intestine

  30. Small Intestine • Mucosa • simple columnar epithelium folded into villi • microvilli on luminal cell surface • crypts of Lieberkuhn • Submucosa • submucosal plexus • duodenal glands (brunner) • Peyer’s Patches (lymphoid tissue in ileum) • Muscularis Externa • inner circular • outer longitudinal • myenteric plexus • Serosa

  31. Large Intestine • ileocecal valve • Gateway to the cecum • cecum • ascending colon • hepatic flexure • transverse colon • splenic flexure • descending colon • sigmoid colon • rectum • anus

  32. Large Intestine • Ileum • Cecum • Appendix • contains a small lumen, when it is unable to clear debris it becomes infected

  33. Large Intestine • Tinea Coli • outer longitudinal layer is reduced to 3 bands that run longitudinally along the colon • Haustra • bulging walls of the colon due to lack of longitudinal muscular support.

  34. Large Intestine • Mucosa • simple columnar epithelium • no villi or microvilli • crypts of Lieberkuhn • goblet cells • Submucosa • usual glands, submucosal plexus, blood vessels • Muscularis Externa • inner circular • outer longitudinal in three bands called tinea coli • myenteric plexus • Serosa

  35. Large Intestine • Rectum • storage are for stool • has 3 valves • controls flow of stool/gas

  36. Large Intestine • anus • stratified squamous epithelium • internal/external anal sphincters

  37. Liver • Main Functions • produces bile • acts as a soap to aid digestion of fat • stores sugar • as glycogen • processes chemicals and toxins • most of the venous return from the digestive system passes through the liver

  38. Liver • Anatomy • Lobes • right • left • caudate • quadrate • Falciform Ligament • divides R and L lobes • suspends liver from diaphragm and ant abd wall • gallbladder

  39. Liver

  40. Liver • Anatomy • hepatic artery • branches off celiac trunk

  41. Liver • Anatomy • Portal Vein • most of the venous return from the digestive system

  42. Liver • Anatomy • Hepatic Vein • returns venous blood to IVC

  43. Liver: Histology • Venous Flow Through Liver • Portal Vein • blood coming in from intestines • Sinusoids • channels between rows of hepatic cells • Central Vein • sinusoids empty into this structure • blood returns to hepatic vein • Bile Canaliculi • bile produced by hepatocytes travel to bile ducts • Portal Triad • portal vein is accompanied by a bile duct and a branch of the hepatic artery

  44. Liver: Histology • Venous Flow Through Liver • Portal Vein • blood coming in from intestines • Sinusoids • channels between rows of hepatic cells • Central Vein • sinusoids empty into this structure • blood returns to hepatic vein • Bile Canaliculi • bile produced by hepatocytes travel to bile ducts • Portal Triad • portal vein is accompanied by a bile duct and a branch of the hepatic artery

  45. Pancreas • Anatomy • snuggled in the C-loop of the duodenum • head • body • tail

  46. Pancreas • functions • produces insulin for control of blood glucose • islets of langerhans • released into bloodstream • produces digestive enzymes • acinar cells • released into duodenum through pancreatic ducts • main (Wirsung) • accessory (Santorini)

  47. Pancreas Histology • functions • lobular structure much like a salivary gland • acini lined with acinar cells • contain zymogen granules that contain digestive enzymes • islets of Langerhans • produce insulin

  48. Pancreas Histology • Pancreatic ducts • secretes bicarb • neutralizes stomach acid

  49. Liver and Pancreas • Bile ducts • R/L hepatic, common hepatic, cystic, common bile duct • the common bile duct and the pancreatic duct usually join just before emptying into the duodenum

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