Bio 449 Lecture 29 Digestive Physiology I Introduction

Bio 449 Lecture 29 – Digestive Physiology I Introduction Components of food Overview of GI system Digestion and absorption Components General structure of the GI "tube" Function and control of the GI tract Physical breakdown of food Mouth Esophagus Stomach Terms to Know Carbohydrate Monosaccharide Disaccharide Polysaccharide Starch Glycogen Readings Lectures 29 -30: Chapter 21 Nov. 17, 2010 Terms to Know Triglyceride Gastrointestinal system Digestion Absorption Serosa Submucosa Mucosa Lumen Peristalisis Motility Mastication Parietal cells Chief cells Goblet cells Pepsin(-ogen) Gastrin Chyme Pyloric sphincter

Components of food

Simple Carbohydrates MONOSACCHARIDES Glucose (dextrose) Fructose Galactose* DISACCHARIDES Sucrose (table sugar) Glucose Fig. 2 -7 + Fructose Maltose Glucose + Glucose Lactose Galactose + Glucose

Complex Carbohydrates POLYSACCHARIDES Animals Chitin (invertebrates only) Yeasts and bacteria Plants Glycogen Cellulose Dextran Starch Glycogen Glucose molecules Fig. 2 -7 Starch

Lipids Glycerol Palmitic acid, a saturated fatty acid G L Y C E R O L Oleic acid, a monounsaturated fatty acid Linolenic acid, a polyunsaturated fatty acid + Fatty acid MONOGLYCERIDE Fatty acid DIGLYCERIDE G L Y C E R O L Fatty acid TRIGLYCERIDE Fatty acid Fig. 2 -8 G L Y C E R O L Fatty acid

Proteins

Overview of GI system

Digestion and absorption Food SECRETION DIGESTION ABSORPTION MOTILITY Lumen of digestive tract Fig. 21 -2 Wall Interstitial fluid Blood

Carbohydrate Digestion Fig. 21 -14

Protein & Fat Digestion Fig. 21 -14

Motility Time zero Bolus Receiving segment Contraction Seconds later Fig. 21 -5 Direction of movement Bolus moves forward No net forward movement

Components of the GI system Oral cavity Salivary glands Esophagus Gallbladder Pancreas Small intestine Rectum Fig. 21 -3 Liver Stomach Large intestine

General structure of the GI tube Mucosa Submucosa Circular muscle Longitudinal muscle Fig. 21 -3 Serosa Submucosal glands

General structure of the GI tube Epithelium Mucosa Lymph vessel Submucosa Muscularis externa Fig. 21 -3 Circular muscle Longitudinal muscle Serosa Artery and vein

Stomach anatomy Esophagus Fundus Diaphragm Body Antrum Pylorus Rugae: Surface folding increases area Fig. 21 -3

Gastric motility

Stomach anatomy Esophagus Fundus Diaphragm Body Antrum Pylorus Rugae: Surface folding increases area Fig. 21 -3

Gastric glands Surface epithelial cells Gastric pit Goblet cells Chief cells Gastric gland Parietal cells