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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Digestive System and Body Metabolism  Digestion  Breakdown of ingested.

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Presentation on theme: "Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Digestive System and Body Metabolism  Digestion  Breakdown of ingested."— Presentation transcript:

1 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Digestive System and Body Metabolism  Digestion  Breakdown of ingested food  Absorption of nutrients into the blood  Metabolism  Production of cellular energy (ATP)  Constructive and degradative cellular activities

2 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Processes of the Digestive System  Mechanical propulsion  Secretion  Digestion - mechanical and chemical breakdown  Absorption  Elimination

3 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings molars (12) premolars (8) canines (4) incisors (8) lower jaw upper jaw Mechanical Processing Teeth break down food

4 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stomach Functions  Acts as a storage tank for food  Mechanical, chemical breakdown of protein begins  Delivers chyme to the small intestine

5 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Stomach  Food must first be well mixed  Rippling peristalsis occurs in the lower stomach Figure 14.15

6 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Digestion in the Small Intestine Figure 14.6 Pancreatic enzymes digest starch, proteins, nucleic acids, fats; reset pH. Gall bladder -

7 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Small Intestine  Peristalsis is the major means of moving food  Segmental movements  Mix chyme with digestive juices  Aid in propelling food

8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorption in the Small Intestine  Site of nutrient absorption into the blood  Villi = Fingerlike structures on the mucosa surface  Microvilli on cells  All increase surface area Figure 14.7a

9 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorption of Proteins and Carbohydrates Figure Amino acids, sugars move by active transport into blood vessels Next stop: liver, where glucose glycogen amino acids protein Excess molecules are converted to fats

10 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorption of Fats Figure Lipids are absorbed into lymph system, which drains into heart Emulsified with bile salts Digested into fatty acids, glycerol With bile salts, diffuse into cells Reassembled into fats, exocytosis

11 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Food Breakdown and Absorption in the Large Intestine  No digestive enzymes are produced  Resident bacteria digest remaining nutrients  Produce some vitamin K and B  Release gases  Water and vitamins K and B are absorbed  Undigested fiber keeps materials moving and is eliminated via feces

12 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Control of Digestive Activity  Regulation dependent on volume and content of food  Nervous system: sight, smell of food, stretch receptors in stomach  Hormones:  Gastrin: stimulates release of gastric juice  Secretin: stimulates pancreas to secrete water and bicarbonate  Cholecystokinin (CCK): signals pancreas to secrete digestive enzymes

13 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nutrition  Carbohydrates: major energy source, simple or complex  Lipids: cell components and energy sources, saturated or unsaturated  Proteins: 20 amino acids  Vitamins: fat soluble and water soluble  Minerals: recommended daily allowance  Fiber

14 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Food Guide Pyramid Figure 14.16

15 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Body Energy Balance  Energy intake = total energy output (heat + work + energy storage)  Energy intake from food oxidation  Energy output  Heat is usually about 60%  Storage energy is in the form of fat or glycogen

16 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Food Intake  Mechanisms that may regulate food intake  Levels of nutrients in the blood  Hormones  Body temperature  Psychological factors

17 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Basal Metabolic Rate  BMR– amount of heat produced by the body per unit of time at rest  Factors that influence BMR  Surface area  Gender  Age – children and adolescents have a higher BMR  thyroxine from thyroid gland

18 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Total Metabolic Rate (TMR)  Total amount of kilocalories the body must consume to fuel ongoing activities  TMR increases with an increase in body activity


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