Transcript Chapter 21
T H I R D E D I T I O N H
UMAN
P
HYSIOLOGY
AN INTEGRATED APPROACH
Dee Unglaub Silverthorn, Ph.D.
Chapter 21 Digestion
PowerPoint ® Lecture Slide Presentation by Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Digestive Anatomy: Overview
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-2a: ANATOMY SUMMARY: The Digestive System
Processes of the Digestive System: Overview
• • • Motility Secretion Absorption • Elimination Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-1: Processes of the digestive system
Digestive Secretions: (
7 L / Day From Tissues into Lumen)
• • • • • • • • Salivary glands Pancreas Water Enzymes Mucus Ions: H + , K + , Na + HCO 3 , Cl Mass Balance (H 2 O) Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-5: Daily mass balance in the digestive system
Digestive Anatomy: Histological Overview
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-2c: ANATOMY SUMMARY: The Digestive System
The GI tract has four layers
• • • • Mucosa • Epithelial cells • Lamina propria • Muscularis mucosae Submucosa muscularis externa Serosa (connective tissue Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Digestive Anatomy: Histological Overview
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-2e: ANATOMY SUMMARY: The Digestive System
Motility: Smooth Muscle Contractions
• • Parastalsis – moves Segmentation – mixes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-4: Contractions in the GI tract
Chemistry of Digestion: Carbohydrates
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-6: Carbohydrate digestion
Chemistry of Digestion: Proteins
• • Proteins enzyme hydrolysis amino acids Enzymes: endopeptidases & exopeptidases Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-7: Endopeptidases and exopeptidases
Chemistry of Digestion: Fats
Figure 21-8: Fat digestion Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Regulating Digestion: CNS and Enteric Nervous System (ENS)
Figure 21-9: The enteric nervous system Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Phases of Digestion: Overview
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-11: Overview of functions in different regions of the digestive system
Chemical and mechanical digestion in the mouth
• • • • Saliva • Lubricates and softens food Salivary amylase • Breaks down starches into smaller carbs Mechanical digestion; mastication Protection • Lysosomes and immunoglobulins kill viruses and bacteria.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Swallowing reflex: Soft Palate & Esophagus
Figure 21-13: The swallowing reflex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gastric Phase: The Stomach
• Storage – sends chyme to the small intestine at a comfortable pace that the duodenum can handle. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Hot Dogs
53 1/2 Nathan's Hot Dogs and Buns 12 minutes Takeru Kobayashi
Digestion in the Stomach
• • • • HCl or gastric acid – parietal C.
• Kills bacteria • Denatures proteins Pepsin – chief C.
• Protein digestion; collagen breakdown Lipase – chief C. 10% of fat digestion Salivary amylase from the mouth upon exposure to low pH is inactivated.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Secretion in the Stomach
• • • • • • Parietal cells – pH-1 Chief cells – inactive pepsinogen active pepsin D cells – somatostatin Enterochromaffin-like (ECL) cells – histamine G cells – the hormone gastrin.
Mucuos cells – mucus and bicarbonate Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
The Stomach Secretions
Figure 21-17: Integration of secretion in the stomach Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Gastric Phase: The Stomach’s chemical barrier
Figure 21-15: The mucus-bicarbonate barrier of the gastric mucosa Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 21-17: Integration of secretion in the stomach Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intestinal Phase: ENDOCRINE RESPONSE
• • The pyloric sphincter sends chyme into the duodenum in spurts.
Acidic chyme in the duodenum stimulates hormone release into the blood of: • Secretin , cholecystokinin , GIP Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intestinal Phase: Reflexes Direct Digestive Action
Figure 21-18: The intestinal phase of gastric function Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intestinal Phase: NEURAL RESPONSE
• • High OsM of the chyme Neural osmoreceptors • Sitmulates neural secretion of an unknown blood borne substance • Inhibits gastric motility • Inhibits acid secretion.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• • •
Intestinal Phase: EXOCRINE RESPONSE
Pancreatic bicarbonate secretions • Secretin stimulates bicarbonate release.
• Neutralize HCl, add bile & enzymes Pancreatic exocrine enzyme secretions • CCK stimulates pancreatic release of inactive enzymes • Figure 21-20 Liver adds bile via gall bladder • CCK stimulates gall bladder contraction • Bile; a non-enzyme • Bile salts • • • Act as detergents Bilirubin cholesterol Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intestinal phase: intestinal secretions
• • Bicarbonate Brush border enzymes • Peptidases • Disaccharidases • Enteropeptidase • Activates inactive pancreatic enzymes • Stationary enymes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Disaccharidases Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Carbohydrate absorption in the intestine
Figure 21-24: Carbohydrate absorption Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Hydrolysis to simple sugars Absorption: transport Na+/ glucose symport Fructose GLUT To ECF capillary
Bile salts and fat digestion
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-23: Bile salts
Let’s remember what “fat” is. . .
• • • Phospholipids Triglycerides cholesterol Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Content Fat* Saturated fat* Protein* Carbohydrates* Fiber
High-fiber, whole grains Fruits & Vegetables
Cholesterol
Diet
Pritikin 10-15% <3% 15-20% 65-75% >40g/d ≥ 5 serv./d ≥ 7 serv./d <100mg U.S. Average 33% 11% 15% 52% 15.6g/d 1.0 serv./d 4.8 serv./d 265mg * = % of calories Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
NHANES IV (1999-2000), NHANES III (1988-94), CDC/NCHS.
U.S.D.A.’s Continuing Survey of Food Intake. (1994-1996).
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-26: Fat digestion and absorption
Lipoproteins: the transport form of cholesterol Liver makes VLDL In the plasma: HDL and LDL
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Intestinal Phase: Fat Digestion & Absorption
• • • Hydrolyzed to small peptides, dipeptides, & amino acids Membrane transport: H + , Na + transcytosis cotransports & To ECF then into capillary Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
The hepatic portal system
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-19: The hepatic portal system
Intestinal Phase: Large Intestine, H 2 O Absorption & Defecation
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-27: Anatomy of the large intestine
Intestinal Phase: Large Intestine Digestion & Absorption
• • Bacterial digest significant amounts of complex carbs and proteins through fermentation.
Most water is reabsorbed Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 21-28: NaCl reabsorption by colonocytes
Digestive Health: Protection & Problems
• • • • • • Immune defense: M-cells, Peyer's patches, lymphocytes Irritable bowel disease – chronic inflammation Diarrhea: leads to dehydration (4 million deaths/yr) • • Osmotic-solutes prevent H 2 O reabsorption Secretory- bacterial toxins ("flush out' pathogens) Vomiting (emesis) can lead to alkalosis Ulcers- H. pylori "heart-burn" acid reflux disease Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings