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Digestion Chapter 23

Digestion Chapter 23. I. Digestion Overview. Two types of digestion 1. Chemical accomplished by enzymatic breakage of chemical bonds, resulting in carbs, lipids, proteins becoming monomers again. 2. Mechanical happens as food is physically broken into smaller and smaller pieces

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Digestion Chapter 23

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  1. Digestion Chapter 23

  2. I. Digestion Overview • Two types of digestion 1. Chemical accomplished by enzymatic breakage of chemical bonds, resulting in carbs, lipids, proteins becoming monomers again. 2. Mechanical happens as food is physically broken into smaller and smaller pieces B. Function is to ingest, break down foodstuffs into monomers, absorb nutrients, water and eliminate the undigestible or harmful.

  3. II.Digestive Organs • Alimentary canal, GI tract is hollow tube (30 feet) located in abdominopelvic cavity • 1-6 = path of food 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small & Large Intestine 6. Rectum & Anus

  4. C.There are Four tunics esophagus to anus. a. mucosa secretes, absorbs and protects (has 3 layers) b. submucosa dense connective w/ elastin, protects & nourishes c. muscularis externa (1)inner layer is circular muscle = peristalsis (2)outer layer is longitudinal = segmentation d. adventia or serosa is visceral peritoneum

  5. 1. Mouth • Entry for digestive system. • Accessory organs are gums, teeth, tongue (lingual frenulum), uvula, soft and hard palate, salivary glands (parotid) tonsils (lingual, palantine, pharyngeal) lips and cheeks

  6. 2. Pharynx • Propels food toward esophagus • Nasopharynx, oropharynx and laryngopharynx

  7. 3. Esophagus a. Food tube (10 inches located behind trachea) moves food by peristalsis. Esophagus is stratified squamous epithelial interspersed w/ goblet cells = mucus to help bolus slide down and a double layer of muscle.

  8. 4. Stomach • Function (1) Mechanical/chemical digestion (2) Secretes enzymes, mucus and hormones (3) Protein digestion (4) Food storage b. Anatomy • greater/lesser curvature • Fundus • Cardiac/pyloric regions and sphincters (superior is gastroesophageal) • Rugae • 3rd layers of muscle is oblique • Greater omentum can get quite large

  9. c. Stomach cells (1) mucous neck cells- acidic mucus, (2) parietal cells (red) secrete HCl (3) chief cells (blue) secrete pepsinogen (4) enteroendocrine cells- release hormones gastrin, CCK, histamine

  10. e. Stomach Histology

  11. 5. Small Intestine a. 3 parts = 6 feet (1) Duodenum 10 inches for absorption and final stages of digestion (2) Jejunum 8 feet (3) Ileum 12 feet (4) ileocecal valve

  12. Small Intestine (5)Sphincter of Oddi controls entry of brush border enzymes, while the bile duct controls entry of bile into Sl. (6) Microvilli (on villi) increase surface area of mucosa. They become less as distance from duodenum increases. (7) Incidence of preyer’s patches increase as distance from duodenum increases. (8) Brunner’s glands in submucosa = mucus

  13. 6.Plicae circulares are deep, permanent folds of mucosa and submucosa that force chyme to spiral thru the lumen, slowing its movement so that absorption can take place

  14. b. Small intestine Histology

  15. (1) Duodenum (crypts)

  16. (a)Duodenum with bile duct from the liver & pancreatic duct from pancreas, is exposed to a plethora of digestive enzymes.

  17. (2) Jejunum

  18. (3) Ileum (preyer’s patches)

  19. 6. Large Intestine, Colon 3 parts a. Ascending b. Transverse c. Descending d. Anatomy (1)Hepatic flexure (2)Splenic Flexure

  20. Colon (3)Colon 3 inches in diameter and 5 feet long. It becomes the sigmoid colon which ends at the rectum (final 6 inches) as feces pass out anus e. Functions (1) to absorb water, BP, creation & elimination of feces

  21. B. Accessory Organs • Teeth • Tongue • Liver* • Gall Bladder • Pancreas* • Salivary* and other *glands

  22. 1. Teeth

  23. Teeth a. Dental formula

  24. Teeth

  25. Tongue ?

  26. 2. Tongue • Moves food, which is now bolus • Initiates swallowing • Sensory = Taste buds

  27. 3. Liver 1.Right lobe of liver 2.Left lobe of liver 4. Round ligament 8. Common bile duct 9. Hepatic artery 10.Portal vein 11.Cystic duct 12.Hepatic duct 13.Gallbladder • Liver is most versatile organ in the body w/ over 200 functions- stores glycogen, makes bile, detoxifies.

  28. b. Liver histology Arranged in 4 lobules

  29. Liver

  30. 4. Gall bladder Stores bile which emulsifies lipids

  31. 5. Pancreas a. Located between stomach and small intestine. b. Alpha cells synthesize & secrete pancreatic juice containing digestive enzymes and hormone glucagon.

  32. c. Pancreas Histology .

  33. 6. Salivary Glands • Secrete salivary amylase starts digestion of starch • Helps bolus stick together

  34. done

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