Download Digestive System: Macromolecule Breakdown and Absorption - Prof. Douglas N. Ishii and more Study notes Biology in PDF only on Docsity! 20 March Macromolecule breakdown Polysaccharides โ simple sugars Proteins โ amino acids Fats โ free fatty acids (FFA) Salivary glands in mouth Amylase breaks down polysaccharides Stomach Pepsinogen, pepsin, HCl break down proteins Liver Bile breaks down fats Pancreas Amylase breaks down polysaccharides Proteases break down proteins (ex. trypsin, carboxypeptidase) Lipases break down fats SI mucosa Sugar enzymes break down polysaccharides Aminopeptidase breaks down proteins Resultant simple compounds can be taken up by cells Simple sugars/amino acids โ hepatic portal vein โ liver โ hepatic vein โ vena cava โ heart Fatty acids โ lacteals โ lymph โ heart Anabolism Fat stored in fat/adipose tissue as triglycerides Amino acids and simple sugars stored in fat/adipose tissue or goes to muscle/liver โ simple sugars stored as glycogen, amino acids stored as protein Catabolism Glycogen โ glucose Proteins โ amino acids Triglycerides โ glycerol/fatty acids Used for glycolysis, citric acid cycle, energy Figure 15.16 Upper part of the GI tract Mouth Chewing Glands Salivary amylase Regulation primarily neural reflexes Figure 15.17 Stomach Digestion Figure 15.21 Figure 15.25 Intestinal phase Secretin Cholecystokinin (CCK) GIP Empty 50% small intestine โ 3 hours Figure 15.26 Cholecystokinin, secretin Act on pancreas, stomach Inhibit stomach action Bicarbonate from pancreas neutralizes acids Secretin acts on duct cells (bicarb) CCK acts on exocrine cells (enzymes); opens sphincter of Oddi โ bile release Figure 15.27 Pancreas secretes inactive enzymes, trypsinogen Trypsinogen โ trypsin Figure 15.28 Hormonal regulation of pancreatic bicarbonate secretin Figure 15.34 โ colon Water/salt absorption, storage 30 โ 40 hours Regulation of GI activities Smooth muscle contractions for movement Peristalsis โ wave of contractions and relaxation โ movement Segmentation โ contraction and relaxation of short segments โ mix Figure 15.23 Peristalsis Peristaltic waves over the stomach Progressive waves of contraction and relaxation Generated by pacemaker cells in longitudinal smooth muscle layer Figure 15.33 Segmentation Rhythmic, stationary contraction and relaxation of intestinal segments Initiated by electrical pacemaker cells in circular smooth muscle layer Segmentation and movement After absorption, segmentation stops and replaced by pattern of peristaltic activity Migrating myoelectric complex Sphincters Upper esophageal Lower esophageal Pyloric Oddi Ileo-cecal Internal anal External anal Peristalsis Propulsion Esophagus, stomach, less in small and large intestine Rhythmic segmentation Mixing Small and large intestine Tonic contraction Functional compartmentalization Sphincters and proximal stomach
