1. Digestion
9.3, 9.4
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2. Digestion
4 steps
ingestion
digestion
absorption
egestion

3. Simple Organisms single-celled organisms
jellyfish, flatworms have gastrovascular cavity
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4. Complex Animals digestive tract with two openings
why is two openings better than one?
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5. Human Digestive System
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6. Image from: http://www.infovisual.info/03/057_en.html

7. Digestion in the Mouth physical digestion with teeth
saliva contains enzyme amylase which digests starch
mucus helps with swallowing
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8. The Esophagus epiglottis closes over the trachea during swallowing
bolus of food moves to stomach due to peristalsis
see animation:
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9. The Stomach sphincters control movement of food in & out of stomach
gastric juice contains enzymes, acid, and mucus
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10. hormone gastrin causes release of pepsinogen
activated by acid to pepsin which digests proteins
bolus becomes chyme
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11. Acid Reflux
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12. Stomach Ulcers
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