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The digestive system

The digestive system. “ The digestive system takes in food, breaks it down into nutrient molecules and absorbs them into the bloodstream, and then rids the body of the indigestible remains.” -E. Marieb. PARTS. 1. Gastrointestinal (GI) tract 2. Accessory organs.

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The digestive system

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  1. The digestive system “ The digestive system takes in food, breaks it down into nutrient molecules and absorbs them into the bloodstream, and then rids the body of the indigestible remains.” -E. Marieb

  2. PARTS 1. Gastrointestinal (GI) tract 2. Accessory organs

  3. Digestive processes(disassembly) • Ingestion • Propulsion a. swallowing b. peristalsis • Mechanical digestion • Chemical digestion • Absorption • Defecation

  4. 1. MOUTH (oral cavity) • Mechanical digestion - teeth/tongue • Chemical digestion - salivary glands: • Contains enzymes

  5. 2. pharynx • Skeletal muscle

  6. 3. esophagus • Propels food using muscles (peristalsis)

  7. 4. stomach • Mechanically and chemically digested into chyme • Limited absorption • Neural control • Stretch receptors activated. Impulse to neurons in stomach wall. Continued gastric gland production and causes peristalsis • Hormonal control: • Food triggers release of gastrin (hormone). Goes in blood. Triggers: • gastric gland juices • constricts sphincter to prevent acid-reflux, • relaxes lower stomach sphincter.

  8. What food type is chemically digested in the mouth? • What is the function of the esophagus?

  9. 5. Small Intestine • Mechanical digestion • Chemical digestion (all) • Done with enzymes from pancreas and bile (formed in liver). • Pancreatic duct and bile duct empty into superior small intestine • Absorption (nutrients)

  10. 6. Large Intestine • Mechanical digestion: • Peristalsis • Mass peristalsis • Chemical digestion: • Bacteria • Absorption: • Water • Some vitamins

  11. ACCESSORY ORGANS

  12. Don’t write: • What is bile? • Bile is a yellow, brown, or green, watery solution containing bile salts, bile pigments, cholesterol, phospholipids and a variety of electrolytes. pH of 7.6 – 8.6

  13. Liver • Produces bile • Bile: part waste product, part digestive secretion (mechanical digestion of lipids) • Metabolism of carbs, lipids, and proteins • Processing of drugs and hormones • Excretion of bilirubin (from heme of old RBCs)

  14. liver summary… • Blood from stomach and intestines passes through liver. When the liver has broken down harmful substances, they are excreted into the bile or blood. Bile by-products enter the intestine and ultimately leave the body in the feces. Blood by-products are filtered out by the kidneys and leave the body in the form of urine.

  15. gallbladder • Stores bile • releases in response to fatty food

  16. PANCREAS • Releases enzymes into duodenum (s. intestine) • has an endocrine function

  17. Summary questions • What mainly happens in the small intestine? • Where is bile made? • What organ stores bile? • In which organ is water mainly absorbed? • What is the circular muscle contraction called that involuntarily moves food through the GI tract? • Where is chyme produced?

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