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1 Structure and Function of the Digestive System Chapter 38.

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Presentation on theme: "1 Structure and Function of the Digestive System Chapter 38."— Presentation transcript:

1 1 Structure and Function of the Digestive System Chapter 38

2 Mosby items and derived items © 2006 by Mosby, Inc. 2 Gastrointestinal Tract Mouth Esophagus Stomach Small intestine Large intestine Rectum Anus

3 Mosby items and derived items © 2006 by Mosby, Inc. 3 Gastrointestinal Tract

4 Mosby items and derived items © 2006 by Mosby, Inc. 4 Gastrointestinal Tract Ingestion of food Propulsion of food and wastes from the mouth to the anus Secretion of mucus, water, and enzymes Mechanical digestion of food particles Chemical digestion of food particles Absorption of digested food Elimination of waste products by defecation

5 Mosby items and derived items © 2006 by Mosby, Inc. 5 Gastrointestinal Tract Histology Mucosa Submucosa Muscularis Serosa or adventitia Enteric plexus Submucosal plexus Myenteric plexus Subserosal plexus

6 Mosby items and derived items © 2006 by Mosby, Inc. 6 Gastrointestinal Tract

7 Mosby items and derived items © 2006 by Mosby, Inc. 7 Mouth Reservoir for chewing and mixing of food with saliva Taste buds Salty, sour, bitter, and sweet Olfactory nerves Teeth 32 permanent teeth

8 Mosby items and derived items © 2006 by Mosby, Inc. 8 Salivary Glands Three pairs Submandibular Sublingual Parotid Saliva Water with mucus, sodium, bicarbonate, chloride, potassium, and salivary α-amylase (carbohydrate digestion) Controlled by sympathetic and parasympathetic fibers

9 Mosby items and derived items © 2006 by Mosby, Inc. 9 Swallowing Esophagus Peristalsis Primary and secondary Upper esophageal sphincter Lower esophageal sphincter Phases Oral and pharyngeal phases Esophageal phase

10 Mosby items and derived items © 2006 by Mosby, Inc. 10 Stomach The stomach is a hollow, muscular organ that stores food, secretes digestive juices, mixes food with the juices, and propels partially digested food (chyme) Muscle layers Longitudinal Circular Oblique

11 Mosby items and derived items © 2006 by Mosby, Inc. 11 Stomach Boundaries Cardiac orifice Pyloric sphincter Pylorus Functional areas Fundus Body Antrum

12 Mosby items and derived items © 2006 by Mosby, Inc. 12 Stomach

13 Mosby items and derived items © 2006 by Mosby, Inc. 13 Gastric Motility Swallowing Gastrin Cholecystokinin Motilin Secretin Gastric emptying

14 Mosby items and derived items © 2006 by Mosby, Inc. 14 Gastric Secretion The stomach secretes large volumes of gastric juices Mucus Acid Enzymes Hormones Intrinsic factor Gastroferrin

15 Mosby items and derived items © 2006 by Mosby, Inc. 15 Gastric Secretion Gastric pits Gastric glands Parietal cells Hydrochloric acid and intrinsic factor Chief cells Pepsinogen G cells Gastrin

16 Mosby items and derived items © 2006 by Mosby, Inc. 16 Gastric Secretion Gastric glands Enterochromaffin-like cells Histamine D cells Somatostatin

17 Mosby items and derived items © 2006 by Mosby, Inc. 17 Gastric Pits and Gastric Glands

18 Mosby items and derived items © 2006 by Mosby, Inc. 18 Gastric Secretion Phases of gastric secretion Cephalic phase Gastric phase Intestinal phase

19 Mosby items and derived items © 2006 by Mosby, Inc. 19 Small Intestine 5 to 6 meters long Three segments Duodenum Jejunum Ileum Ileocecal valve Peritoneum Peritoneal cavity

20 Mosby items and derived items © 2006 by Mosby, Inc. 20 Small Intestine Muscle layers Outerlongitudinal Innercircular Mucosal folds (plica) Villi Microvilli Brush border Lamina propria Lacteal

21 Mosby items and derived items © 2006 by Mosby, Inc. 21 Small Intestine

22 Mosby items and derived items © 2006 by Mosby, Inc. 22 Intestinal Digestion and Absorption Hydrochloric acid Pepsin Pancreatic enzymes Intestinal enzymes Bile salts

23 Mosby items and derived items © 2006 by Mosby, Inc. 23 Intestinal Digestion and Absorption Carbohydrates Proteins Fats Water Electrolytes

24 Mosby items and derived items © 2006 by Mosby, Inc. 24 Intestinal Digestion and Absorption

25 Mosby items and derived items © 2006 by Mosby, Inc. 25 Intestinal Digestion and Absorption

26 Mosby items and derived items © 2006 by Mosby, Inc. 26 Intestinal Digestion and Absorption

27 Mosby items and derived items © 2006 by Mosby, Inc. 27 Intestinal Motility The movements of the small intestine facilitate both digestion and absorption Segmentation Peristalsis Ileogastric reflex Intestinointestinal reflex Gastroileal reflex

28 Mosby items and derived items © 2006 by Mosby, Inc. 28 Large Intestine Cecum Appendix Colon Ascending Transverse Descending Sigmoid Rectum Anus

29 Mosby items and derived items © 2006 by Mosby, Inc. 29 Large Intestine

30 Mosby items and derived items © 2006 by Mosby, Inc. 30 Large Intestine Ileocecal valve OBeirne sphincter Internal anal sphincter External anal sphincter Taenia coli Haustra

31 Mosby items and derived items © 2006 by Mosby, Inc. 31 Gastrointestinal Absorption

32 Mosby items and derived items © 2006 by Mosby, Inc. 32 Intestinal Bacteria The environment of the stomach is relatively sterile because of secreted stomach acid Bile acid secretion, motility, and antibody production keeps bacterial numbers in the duodenum to a minimum There is a low concentration of aerobes in the jejunum Anaerobic bacteria are distal to the ileocecal valve Anaerobes are 95% of the fecal flora in the colon

33 Mosby items and derived items © 2006 by Mosby, Inc. 33 Accessory Organs of Digestion

34 Mosby items and derived items © 2006 by Mosby, Inc. 34 Accessory Organs of Digestion Liver Lobes Separated and attached to the anterior abdominal wall by the falciform ligament Right lobe Caudate and quadrate lobes Left lobe Glisson capsule

35 Mosby items and derived items © 2006 by Mosby, Inc. 35 Liver

36 Mosby items and derived items © 2006 by Mosby, Inc. 36 Hepatic Portal Circulation

37 Mosby items and derived items © 2006 by Mosby, Inc. 37 Liver Liver lobules Hepatocytes Lipocytes Sinusoids Bile canaliculi Common bile duct Major duodenal papilla (sphincter of Oddi)

38 Mosby items and derived items © 2006 by Mosby, Inc. 38 Liver Lobules

39 Mosby items and derived items © 2006 by Mosby, Inc. 39 Liver Kupffer cells Stellate cells Pit cells Disse space

40 Mosby items and derived items © 2006 by Mosby, Inc. 40 Secretion of Bile Bile is an alkaline, bitter-tasting, yellowish green fluid that contains bile salts, cholesterol, bilirubin, electrolytes, and water Bile is formed by hepatocytes and secreted into the bile canaliculi Enterohepatic circulation Recycling of bile salts

41 Mosby items and derived items © 2006 by Mosby, Inc. 41 Enterohepatic Circulation

42 Mosby items and derived items © 2006 by Mosby, Inc. 42 Metabolism of Bilirubin Bilirubin is a by-product of the destruction of aged red blood cells Bilirubin gives bile a greenish black color and produces the yellow tinge of jaundice Unconjugated bilirubin Conjugated bilirubin Urobilinogen

43 Mosby items and derived items © 2006 by Mosby, Inc. 43 Metabolism of Bilirubin

44 Mosby items and derived items © 2006 by Mosby, Inc. 44 Vascular and Hematologic Liver Functions Blood storage Bacterial and foreign particle removal Synthesizes clotting factors Produces bile to absorb fat-soluble vitamins Metabolizes fats

45 Mosby items and derived items © 2006 by Mosby, Inc. 45 Vascular and Hematologic Liver Functions Metabolizes proteins Metabolizes carbohydrates Metabolic detoxification Storage of minerals and vitamins

46 Mosby items and derived items © 2006 by Mosby, Inc. 46 Gallbladder The gallbladder is a saclike organ that lies on the inferior surface of the liver The function of the gallbladder is to store and concentrate bile between meals The gallbladder holds about 90 mL of bile

47 Mosby items and derived items © 2006 by Mosby, Inc. 47 Exocrine Pancreas The exocrine pancreas is composed of acini and networks of ducts that secrete enzymes and alkaline fluids to assist in digestion Pancreatic duct Ampulla of Vater

48 Mosby items and derived items © 2006 by Mosby, Inc. 48 Exocrine Pancreas

49 Mosby items and derived items © 2006 by Mosby, Inc. 49 Exocrine Pancreas Secretions Potassium, sodium, bicarbonate, magnesium, calcium, and chloride Enzymes Trypsinogen, chymotrypsinogen, and procarboxypeptidase Trypsin inhibitor Pancreatic α-amylase Pancreatic lipase

50 Mosby items and derived items © 2006 by Mosby, Inc. 50 Aging and the Digestive Function Tooth enamel and dentin wear down Teeth are lost Periodontal disease Gum recession Osteoporotic bone changes

51 Mosby items and derived items © 2006 by Mosby, Inc. 51 Aging and the Digestive Function Number of taste buds decline Sense of smell diminishes Salivary secretion decreases Decreased esophageal and gastric motility


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