digestion 9.3, 9.4. digestion 4 steps ingestion digestion absorption egestion
TRANSCRIPT
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Digestion
9.3, 9.4
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Digestion
4 steps
• ingestion
• digestion
• absorption
• egestion
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Simple Organisms
• single-celled organisms
• jellyfish, flatworms have gastrovascular cavity
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Complex Animals
• digestive tract with two openings
• why is two openings better than one?
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Human Digestive System
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Digestion in the Mouth
• physical digestion with teeth
• saliva contains enzyme amylase which digests starch
• mucus helps with swallowing
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The Esophagus
• epiglottis closes over the trachea during swallowing
• bolus of food moves to stomach due to peristalsis
• see animation: http://animations.3d4medical.com/Peristalsis-animation_AN2441.html
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The Stomach
• sphincters control movement of food in & out of stomach
• gastric juice contains enzymes, acid, and mucus
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• hormone gastrin causes release of pepsinogen
• activated by acid to pepsin which digests proteins
• bolus becomes chyme
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Acid Reflux
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Stomach Ulcers