Stomach Anatomy and Activity Control of Digestion SI Anatomy Macromolecule Digestion Absorption . Be able to discuss how the three stages of controlling the stomach including excitatory and inhibitory effects. Be able to discuss the anatomy of the SI and accessory organs Be able to discuss how proteins, carbohydrates and fats are digested and absorbed in the SI Handout: Reflexes in the Stomach (in class) Marieb: 23 1

The SI is the Main Digestive Organ 1” in diameter 6-7m in cadaver 2-4m in living person Chemical Digestion Absorption 2

Small Intestine: Gross Anatomy Pyloric sphincter Duodenum*** Jejunum Illeum Ileocecal Valve

Small Intestine is Specialized for Absorption Mucosa has a huge surface area Plicae circulars (1cm) 4

Villi in the Small Intestine Villus (1mm) Capillary bed Lacteal Intestinal Crypts

Microvilli in the Small Intestine Brush Border 1/1000 of mm Enzymes Final protein and carbohydrate digestion

Cells of the Villi Enterocytes Goblet cells Enteroendocrine cells Secretin CCK

Cells of the Crypt Stem Cells Cells replaced every 3-6 days Enzyme Production??? 8

Accessory Glands aide SI Digestion Digestion in SI: 3-6 hours Liver Gall Bladder Pancreas

Pancreas and Liver aid in Digestion 10

Pancreas Aids in Digestion Pancreatic juice: 1200-1500ml/day (pH ~8.5) Pancreatic Enzymes

Pancreatic Enzymes Amylases Zymogens Inactive in the pancreas Activated in the small intestine 12

SI Digestion and Absorption Pancreatic Enzymes Brush Border Transport into cell Transport into capillary bed of villi 13

The Liver is a Versatile Organ Detoxification Activates Hormones and Vitamins Stores Nutrients Produces Bile

The Liver makes Bile Salts Cholesterol Derivatives Emulsifies Fat Placed in Bile: 500-1000ml/day Gall Bladder stores bile

CCK Triggers Bile Release Low pH Fat Proteins Cholecystokinin (CCK) Gall bladder contracts

Absorption of Fats Bile Salts + Fats= Micelles Chylomicrons 17

Absorption of Fats Lacteals Chyle Fats broken down in blood or liver 18

Secretin and CCK Regulate the Pancreas HCl activates release Pancreatic juice CCK Fat activation Enzymes

Absorption in the SI 10-12L  1200ml 99% Nutrients 80% electrolytes and H2O 20

Small Intestine Motility: Segmentation Duodenum 12-14/min Ileum 8-9/min

Small Intestine Motility: Peristalsis Migratory Mobility Model Process repeats itself twice 22