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• jejenum: digestion/

absorption• ileum: absorption

Pancreas

Carbohydrate Digestion

• pancreatic amylase is released into duodenum

• continues breakdown of starch started in the saliva

Pancreatic Secretions

• fat enters duodenum

• cholecystokinin (CCK) is released into blood by cells in duodenum

• CCK causes pancreatic cells to release various substances

pH of Small Intestine

• chyme has pH of about 2.5

• converts prosecretin into secretin, which causes pancreas to release bicarbonate ions (increasing pH to 9.0)

• pepsin is inactivated, protecting the small intestine

Protein Digestion

• trypsinogen released by pancreas

• activated to trypsin by enzyme enterokinase

• trypsin continues to break down proteins into 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 breat down fats into smaller molecules

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 are egested through the anus

Animations…

• Digestion review & quiz:

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html

Let’s review…

Review…

Quizzes:

• http://kidshealth.org/kid/htbw/DSquiz.html

• http://www.softschools.com/quizzes/science/digestive_system/quiz751.html

And finally…science meets art