Unit 3 Notes: The Small Intestine

(1) Regions• Duodenum: (First Chamber)–Approximately 10in long

• Jejunum: (Middle Section)–Approximately 7-8ft long

• Ileum: (Last Section)–Approximately 12ft long

(2) Inside the Duodenum• Secretes Bile, Pancreatic Juice & Bicarbonate:–Bile = Yellow-green solution produced by

the liver, stored in the gallbladder. –Pancreatic Juice = Solution produced by the

pancreas, stored in the pancreas.–Bicarbonate = pH balancing compound

found in the blood.

• Metabolize all remaining proteins and lipids.

(3) About Bile…• Produced by liver, Stored by Gallbladder.

• Contains:–Bile Salts–Waste Pigments (bilirubin)–Cholesterol & Phospholipids

• Function: Emulsify lipids so that they are dispersed throughout water, and can be easily absorbed.

(4) About Pancreatic Juice…• Produced by pancreas.

• Contains:– Carboxypeptidase (Protein Enzyme)– Chymotrypsin (Protein Enzyme)– Amylase (Carbohydrate Enzyme)– Lipases (Lipid Enzymes)– Nucleases (Nucleic Acid Enzymes)

• Function: Metabolize all remaining biomolecules.

(5) Releasing Bile & Pancreatic Juice

• The presence of Lipids & Proteins Release of CCK (cholecystokinin) into bloodstream.

• CCK stimulates the release of bile + pancreatic juice out Sphincter of Oddi.

(6) About Bicarbonate…• Used to maintain pH balance within cells

(and water systems).–Neutralizes acidity of chyme coming

from stomach

• Secreted from Brunner’s Glands along Duodenum Walls.

(7) In The Jejunum & Ileum• Smooth Muscle with millions of microvilli:– Microvilli Absorb Nutrients.– Nutrients directly deposited in blood stream.– Folds in between are called “Crypts of Lieberkuhn”.

• Crypts of Lieberkuhn:– Secrete Lysozymes to eliminate any foreign bacterial

cells.– Secrete Muccin to lubricate and dissolve remaining food

stuff.