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Digestive System What is the function of the digestive system? The - PowerPoint PPT Presentation

Digestive System What is the function of the digestive system? The physical and chemical breakdown of large food molecules into smaller molecules that can be used by cells Diagram the pathway of food through the digestive system


  1. Digestive System

  2. What is the function of the digestive system? • The physical and chemical breakdown of large food molecules into smaller molecules that can be used by cells

  3. Diagram the pathway of food through the digestive system (gastrointestinal tract) (we will complete this part together in class on Friday, November 15 th )

  4. Mechanical and Chemical Digestion • Physical breakdown of • Chemical digestion of large pieces of food into polymers of food into small pieces monomers with the action of enzymes • Occurs in the mouth, • Occurs in the mouth stomach and small and stomach intestine

  5. Mouth and Salivary Glands

  6. Mouth • Mechanically digests food with the teeth when chewing • Salivary glands produce salivary amylase to chemically digest polysaccharides into disaccharides (carbohydrates) • Food is mixed with saliva to form a bolus

  7. Pharynx • Back of the throat • Common passageway for food and air • Leads to a muscular tube called the esophagus

  8. Esophagus

  9. Esophagus • Flap of cartilage called the epiglottis covers the top of the trachea (airway) when food is swallowed • Produces mucus to lubricate food • Lined with involuntary smooth muscle • Pushes food to the stomach with wave-like muscle contractions called peristalsis

  10. Stomach

  11. Stomach • Three layers of smooth muscle, protected by mucus • Mechanically digests food by churning and mixing food with gastric juices ( HCl and pepsinogen ) • Pepsin chemically digests proteins into peptides in the stomach • Mixture of gastric juices and food is called chyme

  12. Hydrochloric Acid • Produced by the stomach • Provides the proper pH (2.0) for the enzyme pepsin to function • Converts inactive pepsinogen into active pepsin

  13. Small Intestine

  14. Small Intestine • Three sections: duodenum, jejunum, ileum • Lined with two layers of smooth muscle and finger-like projections called villi • Villi absorb nutrients from digested food into the bloodstream • Chemical digestion of lipids, proteins and carbohydrates

  15. Small Intestine Enzymes • Produces sucrase , maltase , and lactase – chemical digestion of disaccharides into monosaccharides • Produces peptidase – chemical digestion of peptides into amino acids

  16. Villi of Small Intestine

  17. Large Intestine

  18. Large Intestine • Also known as the colon • No further mechanical or chemical digestion takes place • Absorbs excess water from undigested wastes • Absorbs vitamins, minerals, and other ions

  19. Rectum

  20. Rectum • Last 20 cm of the large intestine • Solid waste (feces) is stored here until it exits the body through the anus

  21. Accessory Organs for Digestion • Liver , pancreas and gall bladder all produce enzymes and/or fluids that assist in the digestion of food • FOOD DOES NOT PASS THROUGH THESE ORGANS

  22. Liver, Gall Bladder and Pancreas

  23. Liver and Gall Bladder • Liver produces bile to emulsify fats (break up large pieces of fat into smaller pieces) • Emulsification is mechanical digestion • Gall bladder is a storage pouch for bile • Bile is secreted into the small intestine through the bile duct

  24. Pancreas • Produces pancreatic juice – consists of sodium bicarbonate and enzymes • Sodium bicarbonate neutralizes the acidic material from the stomach • Enzymes are secreted into the small intestine from the pancreas to assist in digestion

  25. Pancreas Enzymes • Lipase – chemical digestion of lipids into fatty acids and glycerol • Trypsin – chemical digestion of peptides into amino acids • Pancreatic amylase – chemical digestion of disaccharides into monosaccharides

  26. Bozeman Science - Digestion

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