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Download Digestion in the Small and Large Intestine (9.5) File
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Digestion in… …the small & large intestines 9.5 Small Intestine • about 2.5 cm in diameter • up to 7 m in length • duodenum: first 2530 cm: digestion • jejunum: digestion/ absorption • ileum: absorption Accessory Organs pH of Small Intestine • chyme has pH of about 2.5 • prosecretin converts into secretin, which causes pancreas to release bicarbonate ions (increasing pH to 9.0) • pepsin is inactivated in basic conditions, thus secretin protects the small intestine • (secretin also stimulates liver to produce bile, and pancreas to release enzymes) Pancreatic Secretions • chyme enters duodenum • cholecystokinin (CCK) is released into blood by cells in duodenum • CCK causes pancreatic cells to release various substances Carbohydrate Digestion • pancreatic amylase is released into duodenum • continues breakdown of starch started in the saliva Protein Digestion • • • • trypsinogen released by pancreas activated to trypsin by enzyme enterokinase trypsin continues to break down proteins carboxypeptidase & erepsin break down small chains into single amino acids Lipid Digestion • bile is produced in liver & stored in gall bladder and released into the duodenum • bile breaks down large fat globules • lipases secreted by pancreas break down fats into smaller molecules • digested fats are absorbed through lacteals Small Intestine - Absorption Absorption • passive transport (including osmosis) • facilitated diffusion • active transport • nutrients are absorbed in capillary networks Large Intestine • up to 7.6 cm in diameter • about 1.5 m in length Large Intestine • most of the water is absorbed • 500+ species of bacteria produce essential vitamins K and some B. • feces (soft solid) are egested through the anus Resources… • McGraw-Hill Ryerson animation & quiz (good overview, but not a lot of detail about the enzymes & secretions) • Another McGraw-Hill digestion quiz Let’s review… Review… These quizzes are good for reviewing anatomy, but not the enzymes/secretions: • http://kidshealth.org/kid/htbw/DSquiz.ht ml • http://www.softschools.com/quizzes/scie nce/digestive_system/quiz751.html And finally…science meets art
