…the small & large intestines 9.5 Digestion in… …the small & large intestines 9.5

Small Intestine about 2.5 cm in diameter up to 7 m in length duodenum: first 25-30 cm: digestion jejunum: digestion/ absorption ileum: absorption Image from: http://www.gastropatienteducation.com/Gatro_Pat/Pat_Ed_web_pages/Small_Intest/The_Small_Intestine.htmlc

Accessory Organs Liver, pancreas, gall bladder

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 Image from: http://www.edoctoronline.com/medical-atlas.asp?c=4&id=22144 Villi and microvilli increase the surface area for absorption of nutrients.

Absorption passive transport (including osmosis) facilitated diffusion active transport nutrients are absorbed in capillary networks Passive transport is the movement of materials across a cell membrane without the use of energy from the cell. (move from high concentration to low concentration) Facilitated diffusion is the diffusion of molecules across a membrane through transport proteins (embedded in the cell membrane and help diffusion). Active transport is the movement of materials across a cell membrane using energy from the cell (move from lower concentration to higher concentration)

Large Intestine up to 7.6 cm in diameter about 1.5 m in length Image from: http://www.webmd.com/digestive-disorders/large-intestine

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…

Image from: http://www.merriam-webster.com/art/med/digestio.htm

Review… These quizzes are good for reviewing anatomy, but not the enzymes/secretions: http://kidshealth.org/kid/htbw/DSquiz.html http://www.softschools.com/quizzes/science/digestive_system/quiz751.html

And finally…science meets art Image from: http://www.neatorama.com/2008/09/15/wim-delvoye-worlds-most-badass-artist/ Belgian conceptual artist Wim Delvoye created a machine that digests food…and produces feces.