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Lab Exercise 26

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  1. Lab Exercise 26 Anatomy of the Digestive System Portland Community College BI 233

  2. Digestive System • Alimentary Canal: hollow tube extending from mouth to anus • Technically outside the body • Covered with mucous membrane • Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas

  3. Digestion • Process by which foods are broken down into simpler forms so that nutrients can be delivered to all areas in the body. • Ingestion chewing muscular actions Enzymatic breakdown absorption excretion

  4. Membranes • Parietal Peritoneum: Covers the wall of the abdominal cavity • Visceral Peritoneum: Covers the outside of all the abdominal organs • Mesentery: a fold of peritoneum attaching the small intestine to the posterior abdominal wall • Greater Omentum: Thick sheet of tissue (lots of fat) that hangs off the greater curvature of the stomach • Lesser Omentum: Anchors the liver to the lesser curvature of the stomach • Mesocolon: a fold of peritoneum attaching the colon to the posterior abdominal wall

  5. Membranes

  6. Membranes

  7. Mesentery

  8. Greater Omentum

  9. Oral Cavity • The lips surround the anterior opening. • Consist of skeletal muscle covered with skin. • Posteriorly, the fauces is the opening leading to the oropharynx. • Cheeks form the lateral walls. • The tongue occupies the floor

  10. Tongue • Composed of skeletal muscle. • Intrinsic tongue muscles are important for changing the shape of the tongue while speaking and swallowing. • Extrinsic tongue muscles are connected to hyoid bone and styloid process of temporal bone.

  11. Teeth • Gingiva is the mucous membrane (gums) • Each region of a tooth is identified according to its relationship to the gingival margin (gum line) • Crown is visible portion • Root is below gum line • Neck is between

  12. Incisor (cutting) Canine (tearing) Premolar (tearing and grinding) Molar (grinding) Teeth Adults have 32 teeth Children have 20 deciduous teeth

  13. Salivary Glands • Parotid: Primarily serous with salivary amylaseSublingual: Primarily secrete mucous • Submandibular: Smallest of the salivary glands secrete both serous and mucous fluids

  14. Salivary Gland Histology Demilune

  15. Submandibular salivary gland Mucus Acini Serous Acini Duct Serous Acini Demilune

  16. Extends from pharynx through the diaphragm at the esophageal hiatus to the lower esophageal sphincter into the stomach Esophagus Body Diaphragm Lower Esophageal Sphincter

  17. Stomach Rugae

  18. Position of Stomach

  19. Small Intestine: Gross Anatomy • Runs from pyloric sphincter to the ileocecal valve • Has three subdivisions: duodenum, jejunum, and ileum • The bile duct and main pancreatic duct: • Join the duodenum at the hepatopancreatic ampulla • Are controlled by the sphincter of Oddi • The jejunum extends from the duodenum to the ileum • The ileum joins the large intestine at the ileocecal valve

  20. Small Intestine Minor papilla PlicaCircularis Ileum DuodenumC-Loop Major papilla

  21. Pancreas Head Body Tail Common Bile Duct Accessory Duct Pancreatic Duct

  22. Small Intestine: Ileum Ileocecal valve

  23. Large Intestine • Is subdivided into the • Cecum • Appendix • Colon • Rectum • Anal canal • The saclike cecum: • Lies below the ileocecal valve in the right iliac fossa • Contains a wormlike vermiform appendix Ileum

  24. Hepatic Portal Vein Aorta Large Intestine Superior Mesenteric Artery Inferior Mesenteric Artery Ileocecal valve is in here Cecum Appendix Ileum

  25. Has distinct regions: ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, and sigmoid colon The sigmoid colon joins the rectum The anal canal, the last segment of the large intestine, opens to the exterior at the anus Colon

  26. Transverse Colon Colon Splenic Flexure Hepatic Flexure Descending Colon Ascending colon Rectum Sigmoid Colon Anal Canal

  27. Valves and Sphincters of the Rectum and Anus • Three valves of the rectum stop feces from being passed with gas • The anus has two sphincters: • Internal anal sphincter composed of smooth muscle • External anal sphincter composed of skeletal muscle • These sphincters are closed except during defecation

  28. Structure of the Anal Canal

  29. Biliary Tree

  30. Liver • The largest gland in the body • Superficially has four lobes – right, left, caudate, and quadrate • The falciform ligament: • Separates the right and left lobes anteriorly • Suspends the liver from the diaphragm and anterior abdominal wall

  31. GI Tract Histology • All of the hollow organs have the same basic 4 layers. 1. Mucosa (Lumen side) • Epithelial layer (remember from 231: stratified squamous, columnar ect…) • Lamina Propria: Base made of loose areolar connective tissue • Muscularis Mucosa: Base of smooth muscle fibers 2. Submucosa • Dense irregular connective tissue • This is where the blood vessels, nerves and the glands are.

  32. GI Tract Histology 3. Muscularis Externa • The main smooth muscle layer used for peristalsis • Longitudinal and Circular layers with myenteric plexus (parasympathetic ganglion) in between 4. Serosa (Abdominal cavity side) • Epithelial layer (usually simple squamous) • Also known as the visceral peritoneum

  33. GI Tract Histology

  34. Mucosa Lumen Epithelial Cells Mucosa Lamina Propria(Loose areolar CT) Muscularis Mucosa Submucosa (Dense irregular CT)

  35. Myenteric Plexus in Muscularis Externa Longitudinal Muscle Layer Satellite Cell Myenteric Plexus Neuron Cell Body Circular Muscle Layer

  36. Esophagus Histology • Mucosa • Epithelium • Non-keratinized stratified squamous

  37. Esophagus Histology • Submucosa (#2) • Esophageal glands • Vessels • Submucosal Plexus

  38. Esophagus Histology • 3. Muscularis Externa • Upper 1/3=Skeletal • Middle 1/3=Blend • Lower 1/3=Smooth • 4. Adventitia (Rest of GI tract: Serosa) • Coarse Fibrous CT: binds/anchors Skeletal Muscle Smooth Muscle

  39. StomachHistology • 4 layers: • Mucosa (inside layer) • Simple columnar epithelium • Submucosa • Muscularis Externa smooth muscle in 3 layers • Serosa (visceral peritoneum)

  40. Stomach Histology:Mucosa (Inside layer) • Mucosa: Simple columnar epithelium

  41. Stomach Mucosa • Mucous neck cells • Alkaline mucus • Parietal cells • HCL • Intrinsic factor • Chief cells • Pepsinogen • Gastric lipase • G cells (in antrum) • Gastrin

  42. Stomach Mucosa Mucus Neck Cells Gastric Pits

  43. Lamina propria Lumen of pit Parietal cell Chief cell Entroendocrine (G cell)

  44. Small Intestine: Histology • Structural modifications of the small intestine wall increase surface area • Plica circularis: Transverse folds on the mucosa • Villi: Fingerlike extensions of the mucosa • Microvilli (Brush border): Tiny projections of absorptive mucosal cells’ plasma membranes

  45. Small Intestine: Plica Circularis

  46. Small Intestine Histology: Mucosa • Plicae circulares: Large deep, permanent folds of the mucosa and submucosa. • Slow the movement of chyme (more time for digestion/absorption) and increase the surface area.