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The Digestive System

The Digestive System. Small Intestine. Longest part of alimentary canal (13-23 feet!) Goes from pyloric sphincter to ileocecal valve Mesentery helps support it in place Bile and pancreatic enzymes meet to finish chemical digestion Most food digestion and absorption takes place here

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The Digestive System

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  1. The Digestive System

  2. Small Intestine • Longest part of alimentary canal (13-23 feet!) • Goes from pyloric sphincter to ileocecal valve • Mesentery helps support it in place • Bile and pancreatic enzymes meet to finish chemical digestion • Most food digestion and absorption takes place here • Food spends about 3-5 hours here

  3. Divisions of Small Intestine • Ileocecal valve • Split between small & large intestine • Dogs Just Itch! • Duodenum • Attached to the stomach • Curves around the head of the pancreas • Where bile & pancreatic enzymes enter • Jejunum • Middle portion • Ileum • Last portion

  4. Small Intestine • Pancreatic Ducts • Emit pancreatic enzymes from pancreas to help with chemical digestion • Bile Duct • Emits bile from liver/gallbladder to help with chemical digestion

  5. Small Intestine • Microvilli / Villi / Circular Folds • Structures that help to increase surface area to help in absorption of nutrients into bloodstream

  6. Small Intestine • Peyer’s patches • Lymphatic tissue that prevents bacteria in digesting food from entering bloodstream

  7. Large Intestine • Larger in diameter, shorter in length (approx. 5 feet in length) • Extends from ileocecal valve to anus • Dries out indigestible food residue by absorbing water, and eliminates from body as feces • Haustra (pouches) contract to move food along • Food spends about 10-24 hours here!

  8. Large Intestine • Cecum • First part of large intestine • Looks like a pouch • Has “appendix” hanging off • Provides a place for bacteria (good and bad!) to accumulate. If too much accumulates, you can develop appendicitis.

  9. FYI: The Appendix • The appendix has provided a lot of uncertainty among the medical community! While some believe it is a remnant of embryological development, others believe it is a safe-haven for beneficial bacteria. If illness takes over and digestive bacteria are flushed out (via diarrhea), the appendix can provide a place for “replacement” bacteria to be stored.

  10. Colon • Ascending Colon • Travels up right side from cecum to right colic flexure • Transverse Colon • Travels across abdominal cavity to left colic flexure • Descending Colon • Travels down left side to sigmoid colon

  11. Large Intestine • Sigmoid Colon • S-shaped part of Large Intestine in pelvis, curves to form the rectum • Rectum / Anal Canal / Anus • End of the large intestine • Anal canal has sphincters to help open anus during defecation • Anus opens to exterior

  12. Goblet Cells • Large Intestine doesn’t need villi – no absorption of nutrients happens here! • However, does have goblet cells • Produce mucus to help in the passage of dried-out feces

  13. http://video.about.com/ibdcrohns/Digestion.htm

  14. Accessory Digestive Organs • Assists Alimentary Canal in digestive process • Includes… • Salivary glands • Teeth • Pancreas • Liver • Gallbladder

  15. Salivary Glands • Salivary Glands • Empties saliva into mouth • Saliva is 98% water, containing enzymes & bacteria inhibitors • Moistens & helps food to bind together (bolus) • Salivary Amylase enzyme begins digestion (starch) • Saliva also lubricates & protects teeth, tongue, and mouth tissue • Three pairs of salivary glands include…

  16. Salivary Glands • Parotid glands • Submandibular glands • Sublingual glands

  17. Teeth • Teeth • Job of teeth is mastication (chewing) - mechanical breakdown of food • Complete the actions of cutting, tearing, and grinding

  18. Pancreas • Gland that produces a wide spectrum of digestive enzymes that break down all categories of food • Enzymes are secreted into the duodenum (first part of small intestine) • Alkaline (basic) fluid introduced with enzymes neutralizes acidic chyme • Endocrine products of pancreas include: • Insulin • Glucagons • (we’ll talk about these with the endocrine system!!!)

  19. Liver • Largest gland in the body • Located on the right side of the body under the diaphragm • Consists of four lobes suspended from the diaphragm • Main job is to produce bile

  20. Bile • Produced by cells in the liver • Composition • Bile salts • Bile pigments (bilirubin – dead RBC’s – what makes feces brown!) • Cholesterol • Phospholipids • Electrolytes • Only bile salts and phospholipids aid digestive process • Emulsify fats by breaking them down into smaller pieces, providing more surface area for enzymes to work on

  21. Gallbladder • Liver connected to the gall bladder via the common hepatic duct • Sac found in inferior surface of liver • Stores bile from the liver & concentrates it by removal of water • Bile is introduced into the duodenum through the bile duct in the presence of fatty food • If bile stored for too long, or if too much water is removed, gallstones can form

  22. Digestion • The entire process of digestion can take anywhere from 16-48 hours • Most of this time will be spent in the small intestine • Ingestion of approximately 2000 mL of food & drink will result in the defecation of approximately 150 mL of feces

  23. Absorption of water and nutrients (goblet cells) Absorption of water

  24. Chemical Digestion: Carbohydrates • Break down into simple sugars (monosaccharides, such as glucose) • Remember, carbs are polysaccharides! • Digestion: • In Mouth: salivary amylase digests starches • In Small Intestine: Pancreatic enzymes, and additional secretions from walls of small intestine continue breakdown

  25. Chemical Digestion: Proteins • Break down into amino acids • Digestion: • In Stomach: HCl causes proteins to denature (untangle), Pepsin begins breakdown process • In Small Intestine: Pancreatic enzymes continue breakdown

  26. Chemical Digestion: Fats • Broken down into fatty acids and glycerol • Digestion: • In Small Intestine: Bile salts help to emulsify large fats, Pancreatic enzymes breaks down the fats into smaller components

  27. Chemical Digestion: Fats

  28. Role of Bacteria • The bacterial flora of the large intestine consist of: • Bacteria surviving the small intestine that enter the cecum and • Those entering via the anus • These bacteria: • Colonize the colon • Ferment indigestible carbohydrates • Release gases (flatus – methane and hydrogen sulfide) • Synthesize vitamins B and K

  29. http://video.about.com/pediatrics/Appendicitis.htm • http://video.about.com/heartburn/GERD.htm • http://video.about.com/highbloodpressure/Renovascular-Hypertension.htm

  30. Conditions of the digestive systemGastric Surgery for weight loss • Gastric Band: An inflatable band is placed around the stomach to create a small pouch. • http://video.about.com/weightloss/Laparoscopic-Gastric-Banding.htm • Roux En Y: Stomach is now a small pouch and can hold only 1 ounce of food at a time. • http://video.about.com/weightloss/Biliopancreatic-Diversion.htm

  31. Diverticulitis • Small pouches in the large intestine become clogged and inflamed with bacteria & feces. • Typically treated with antibiotics however sometimes may need surgery to remove infected gut.

  32. Bowel Obstruction • Partial or complete blockage of the small or large bowel. • Causes: severe constipation, tumors, scar tissue, or twisting or narrowing of the intestines. • Treatment: Laxatives or surgery

  33. Ulcerative Colitis/ Crohn’s Disease • Disease of the intestines causing ulcers & inflammation. • Ulcerative Colitis is less invasive and only affects the large intestine • Crohn’s disease is more severe and can cause ulcers throughout the digestive tract.

  34. Gastric Ulcers • Also known as peptic ulcer. • Inflammation in either the stomach or the duodenal mucosa, with extension beyond the submucosa into the muscularis mucosa. • Most commonly caused is bacteria called Helicobacter pylori. • Other causes include medication induced or increase production of gastric secretions.

  35. Alternative Nutrition • Enteral Nutrition: • Also known as tube feeding • Given via a tube through the mouth/nose/stomach and extends into either the stomach or intestines. • Special formulas used containing all nutrients. • “If the gut works, use it” But if it doesn’t work use Total Parental Nutrition (TPN) • Nutrition via blood.

  36. Celiac Disease • Sometimes called “Slick Gut” because the lining of the small intestines becomes so inflamed food is unable to be absorbed and passes right through • Inflammation is caused by an allergy to gluten, a protein found in wheat. • Treatment: AVOID WHEAT! The following foods contain wheat: Bread, Pasta, Oats, Barley, Cookies, Cakes, Most Cereals, Most Processed Foods, Many Spices… And many more…

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