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Structure and Function of the Digestive System

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Presentation on theme: "Structure and Function of the Digestive System"— Presentation transcript:

1 Structure and Function of the Digestive System
Chapter 38

2 Gastrointestinal Tract
Mouth Esophagus Stomach Small intestine Large intestine Rectum Anus

3 Gastrointestinal Tract

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 Gastrointestinal Tract
Histology Mucosa Submucosa Muscularis Serosa or adventitia Enteric plexus Submucosal plexus Myenteric plexus Subserosal plexus

6 Gastrointestinal Tract

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 Salivary Glands Three pairs Saliva Submandibular Sublingual Parotid
Water with mucus, sodium, bicarbonate, chloride, potassium, and salivary α-amylase (carbohydrate digestion) Controlled by sympathetic and parasympathetic fibers

9 Swallowing Esophagus Peristalsis Upper esophageal sphincter
Primary and secondary Upper esophageal sphincter Lower esophageal sphincter Phases Oral and pharyngeal phases Esophageal phase

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 Stomach Boundaries Functional areas Cardiac orifice Pyloric sphincter
Pylorus Functional areas Fundus Body Antrum

12 Stomach

13 Gastric Motility Swallowing Gastrin Cholecystokinin Motilin Secretin
Gastric emptying

14 Gastric Secretion The stomach secretes large volumes of gastric juices
Mucus Acid Enzymes Hormones Intrinsic factor Gastroferrin

15 Gastric Secretion Gastric pits Gastric glands Parietal cells
Hydrochloric acid and intrinsic factor Chief cells Pepsinogen G cells Gastrin

16 Gastric Secretion Gastric glands Enterochromaffin-like cells D cells
Histamine D cells Somatostatin

17 Gastric Pits and Gastric Glands

18 Gastric Secretion Phases of gastric secretion Cephalic phase
Gastric phase Intestinal phase

19 Small Intestine 5 to 6 meters long Three segments Peritoneum Duodenum
Jejunum Ileum Ileocecal valve Peritoneum Peritoneal cavity

20 Small Intestine Muscle layers Mucosal folds (plica) Villi Microvilli
Outer—longitudinal Inner—circular Mucosal folds (plica) Villi Microvilli Brush border Lamina propria Lacteal

21 Small Intestine

22 Intestinal Digestion and Absorption
Hydrochloric acid Pepsin Pancreatic enzymes Intestinal enzymes Bile salts

23 Intestinal Digestion and Absorption
Carbohydrates Proteins Fats Water Electrolytes

24 Intestinal Digestion and Absorption

25 Intestinal Digestion and Absorption

26 Intestinal Digestion and Absorption

27 Intestinal Motility The movements of the small intestine facilitate both digestion and absorption Segmentation Peristalsis Ileogastric reflex Intestinointestinal reflex Gastroileal reflex

28 Large Intestine Cecum Appendix Colon Rectum Anus Ascending Transverse
Descending Sigmoid Rectum Anus

29 Large Intestine

30 Large Intestine Ileocecal valve O’Beirne sphincter
Internal anal sphincter External anal sphincter Taenia coli Haustra

31 Gastrointestinal Absorption

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 Accessory Organs of Digestion

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 Liver

36 Hepatic Portal Circulation

37 Liver Liver lobules Hepatocytes Lipocytes Sinusoids Bile canaliculi
Common bile duct Major duodenal papilla (sphincter of Oddi)

38 Liver Lobules

39 Liver Kupffer cells Stellate cells Pit cells Disse space

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 Enterohepatic Circulation

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 Metabolism of Bilirubin

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 Vascular and Hematologic Liver Functions
Metabolizes proteins Metabolizes carbohydrates Metabolic detoxification Storage of minerals and vitamins

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 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 Exocrine Pancreas

49 Exocrine Pancreas Secretions Enzymes
Potassium, sodium, bicarbonate, magnesium, calcium, and chloride Enzymes Trypsinogen, chymotrypsinogen, and procarboxypeptidase Trypsin inhibitor Pancreatic α-amylase Pancreatic lipase

50 Aging and the Digestive Function
Tooth enamel and dentin wear down Teeth are lost Periodontal disease Gum recession Osteoporotic bone changes

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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