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Chapter 19 The Digestive System

Chapter 19 The Digestive System. Key Terms. absorption esophagus pancreas bile gallbladder peptic ulcer chyle hydrolysis peristalsis chyme ingestion peritoneum defecation intestine saliva deglutition lacteal sphincter digestion liver stomach duodenum mastication villi

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Chapter 19 The Digestive System

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  1. Chapter 19 The Digestive System

  2. Key Terms absorption esophagus pancreas bile gallbladder peptic ulcer chyle hydrolysis peristalsis chyme ingestion peritoneum defecation intestine saliva deglutition lacteal sphincter digestion liver stomach duodenum mastication villi emulsify mesentery

  3. General Structure and Function of the Digestive System General Functions • Digestion • Absorption • Elimination Divisions • Digestive tract • Accessory organs

  4. Figure 19-1 The digestive system. Which accessory organs of digestion secrete into the mouth?

  5. General Structure and Function of the Digestive System (cont.) Peritoneum • Lines the abdominopelvic cavity; covers abdominal organs • Layers of the peritoneum • Parietal • Visceral • Subdivisions • Mesentery • Mesocolon • Greater omentum • Lesser omentum

  6. General Structure and Function of the Digestive System (cont.) The Wall of the Digestive Tract • Mucosal membrane, or mucosa • Submucosa • Smooth muscle, the muscularis externa • Serous membrane, or serosa

  7. Figure 19-3 Wall of the digestive tract. What type of tissue is between the submucosa and the serous membrane in the digestive tract wall?

  8. General Structure and Function of the Digestive System (cont.) ? Pop Quiz 19.1 Which of the following is the correct order from the outermost to innermost layer? A) Submucosa, serous membrane, smooth muscle, mucous membrane B) Smooth muscle, serous membrane, mucous membrane, submucosa C) Serous membrane, smooth muscle, submucosa, mucosa D) Mucous membrane, submucosa, smooth muscle, serous membrane

  9. General Structure and Function of the Digestive System (cont.) ? Pop Quiz Answer 19.1 Which of the following is the correct order from the outermost to innermost layer? A) Submucosa, serous membrane, smooth muscle, mucous membrane B) Smooth muscle, serous membrane, mucous membrane, submucosa C) Serous membrane, smooth muscle, submucosa, mucosa D) Mucous membrane, submucosa, smooth muscle, serous membrane

  10. Organs of the Digestive Tract (cont.) • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine

  11. Organs of the Digestive Tract (cont.) The Mouth • Also called oral cavity, processes food by: • Ingestion • Mastication • Mixing with saliva • Deglutition • Tongue

  12. Figure 19-4 Gastrointestinal motility. Which type of motility would be most useful in the esophagus, where the contents should move quickly?

  13. Organs of the Digestive Tract (cont.) The Teeth • Sets of teeth • Deciduous • Permanent • Types of teeth • Incisors • Cuspids • Molars • Six-year molars • Premolars • Third molars or wisdom teeth

  14. Organs of the Digestive Tract (cont.) The Teeth (cont.) • Parts of a tooth • Dentin • Crown • Enamel • Root • The gum • Gingiva

  15. Figure 19-5 The mouth and teeth.

  16. Organs of the Digestive Tract (cont.) The Pharynx • Also called the throat • Divisions • Oropharynx • Nasopharynx • Laryngopharynx • Soft palate • Uvula

  17. Organs of the Digestive Tract (cont.) The Esophagus • Muscular tube. • Food is lubricated with mucus. • Peristalsis. • No digestion occurs here. • Passes through esophageal hiatus of the diaphragm to join stomach.

  18. Organs of the Digestive Tract (cont.) The Stomach • Structure • Greater curvature • Lesser curvature • Fundus • Body • Pylorus • Sphincters • Lower esophageal sphincter (LES) • Pyloric

  19. Organs of the Digestive Tract (cont.) The Stomach (cont.) • Functions • Storage pouch • Rugae • Secrete substances to form gastric juice • Hydrochloric acid prepares proteins for digestion. • Pepsin digests proteins. • Delivery of chyme to the small intestine

  20. Organs of the Digestive Tract (cont.) The Small Intestine • Subdivisions of the small intestine • Duodenum • Jejunum • Ileum • Functions of the small intestine • Secretion • Motility • Digestion • Absorption

  21. Figure 19-7 The intestines.

  22. Organs of the Digestive Tract (cont.) The Large Intestine • Subdivisions of the large intestine • Cecum • Ileocecal valve • Appendix • Ascending colon • Transverse colon • Descending colon • Sigmoid colon • Rectum • Anal canal • Anus

  23. Organs of the Digestive Tract (cont.) • Functions of the large intestine • Production of mucus • Reabsorb some water • Form feces (stool) • Defecation

  24. Organs of the Digestive Tract (cont.) ? Pop Quiz 19.2 Which organ receives food flowing through the pyloric sphincter? A) Stomach B) Jejunum C) Duodenum D) Esophagus

  25. Organs of the Digestive Tract (cont.) ? Pop Quiz Answer 19.2 Which organ receives food flowing through the pyloric sphincter? A) Stomach B) Jejunum C) Duodenum D) Esophagus

  26. The Accessory Organs (cont.) • Release secretions through ducts into the digestive tract. • Salivary glands open to mouth. • Other organs release secretions into the duodenum: • Liver • Gallbladder • Pancreas

  27. The Accessory Organs (cont.) Salivary Glands • Functions -Secrete saliva • Moistens food • Facilitates mastication and deglutition • Helps keep teeth and mouth clean • Three pairs: • Parotid glands • Submandibular glands • Sublingual glands

  28. The Accessory Organs (cont.) The Liver • Structure of the liver • Largest accessory organ • Right, left lobes • Portal vein • Hepatic artery

  29. The Accessory Organs (cont.) The Liver (cont.) • Functions of the liver • Manufactures bile • Controls blood glucose levels • Modifies fats • Stores some vitamins, iron • Forms blood plasma proteins • Destroys old red blood cells • Synthesizes urea • Detoxifies harmful substances

  30. The Accessory Organs (cont.) The Liver (cont.) • Bile • Manufactured in the liver. • Bile leaves the liver by ducts. • Common hepatic duct • Cystic duct • Common bile duct

  31. Figure 19-9 Accessory organs of digestion. Into which part of the small intestine do these accessory organs secrete?

  32. The Accessory Organs (cont.) The Gallbladder • Muscular sac • Located on inferior surface of the liver • Stores bile

  33. The Accessory Organs (cont.) The Pancreas • Gland that produces enzymes • Releases large amounts of sodium bicarbonate (NaHCO3) • Also functions as an endocrine gland

  34. Enzymes and the Digestive Process (cont.) • Fundamental chemical process of digestion • Enzymes • Required for digestion • Catalysts • Highly specific proteins

  35. Enzymes and the Digestive Process (cont.) Role of Water • Hydrolysis • Seven liters of water secreted into the digestive tract daily • Produces digestive juices • Dilutes food • Used in the chemical process of digestion

  36. Figure 19-10 Hydrolysis.

  37. Digestion, Step by Step Digestion in the Mouth • Chews food, mixes with saliva • Some starches changed to sugars via salivary amylase Digestion in the Stomach • Secretes HCl, enzymes • Denatures proteins • Secretes mucus • Forms chyme

  38. Digestion, Step by Step (cont.) Digestion in the Small Intestine Most digestion occurs in the duodenum. • Fats • Carbohydrates • Proteins • Nucleic acids

  39. Absorption (cont.) • Villi in mucosa of the small intestine: • Arteriole and venule bridged with capillaries • Capillaries absorb: • Simple sugars • Small proteins • Amino acids • Simple fatty acids • Water • Portal system transports nutrients to the liver.

  40. Absorption (cont.) • Absorption of fats • Lacteals absorb fat. • Fat/lymph mixture (chyle) drains from the small intestine. • Chyle merges with lymphatic circulation, enters blood in veins near the heart. • The liver further processes absorbed fats.

  41. Absorption (cont.) • Absorption of vitamins and minerals • Vitamins and minerals are absorbed from the small intestine. • Minerals and some vitamins mix with water and are absorbed directly into the blood. • Other vitamins are incorporated in fats and absorbed along with fats. • Vitamin K and some B vitamins are produced by bacterial action in the colon and are absorbed from the large intestine.

  42. Figure 19-11 Carbohydrates. Name the two monosaccharide components of sucrose.

  43. Enzymes and the Digestive Process (cont.) ? Pop Quiz 19.3 Which enzyme digests carbohydrates? A) Amylase B) Pepsin C) Lipase D) Trypsin

  44. Enzymes and the Digestive Process (cont.) ? Pop Quiz Answer 19.3 Which enzyme digests carbohydrates? A) Amylase B) Pepsin C) Lipase D) Trypsin

  45. Control of Digestion and Eating (cont.) Control of Digestion Two types of control over digestion—nervous and hormonal • Nervous control of digestion • Parasympathetic stimulation increases activity • Sympathetic stimulation decreases activity • Hormonal control of digestion • Digestive organs produce hormones • Gastrin • Gastricinhibitory peptide (GIP) • Secretin • Cholecystokinin (CCK)

  46. Control of Digestion and Eating (cont.) Control of Hunger and Appetite • Hunger • Desire for food • Regulated by hypothalamic centers • Respond to nutrient levels • Satisfied by adequate meal • Appetite • No relationship to need for food • May not be satisfied by adequate meal

  47. Control of Digestion and Eating (cont.) • Short-term regulation of hunger • Hypothalamus induces hunger sensations • Ghrelin hormone • Food consumption • Long-term regulation of body weight • Leptin hormone produced by adipocytes

  48. Figure 19-12 Regulation of food intake.

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