BIOM2012 Systems Physiology Gastrointestinal Lecture Notes PDF

BIOM2012: Systems Physiology Module: Gastrointestinal System - Lecture 2+3 Ben Weger, PhD ([email protected]) Institute of Molecular Bioscience Physiology of Circadian Rhythms  BIOM2012 GI Module Lecture 1: O...

BIOM2012: Systems Physiology Module: Gastrointestinal System - Lecture 2+3 Ben Weger, PhD ([email protected]) Institute of Molecular Bioscience Physiology of Circadian Rhythms  BIOM2012 GI Module Lecture 1: Overview of digestion and absorption processes in the GIT, phases of gastric secretions, secretions of the Gastrointestinal system and their functions, digestive enzymes Lectures 2 & 3: The remaining GI system secretions and their functions, the intestinal phase of gastric secretion, motility in the GIT, the enteric nervous system Lecture 4: Liver anatomy and structure, functions of the liver, circadian clock and the Gastrointestinal system All content covered in the lectures is examinable unless stated otherwise. In some lectures within the GI module, videos are provided to supplement the material. Any additional content in the videos that is not covered in the slides is not examinable. Organs of the Digestive System Major Organs of the Accessory Organs of Digestive Tract the Digestive System Teeth Oral Cavity (Mouth): Pharynx (throat): Tongue Salivary Glands Esophagus: Liver Stomach: Small Intestine Gallbladder (Duodenum, Jejenum, Ileum ) Pancreas Large Intestine (Colon, Cecum/Appendix, Colon Rectum, Anus) Rectum 3 Four processes of the digestive system in different parts of the GI tract Organs of the Digestive System Major Organs of the Accessory Organs of Digestive Tract the Digestive System Teeth Oral Cavity (Mouth): Pharynx (throat): Tongue Salivary Glands Esophagus: Liver Stomach: Small Intestine Gallbladder Pancreas Large Intestine Colon Rectum 5 Challenges of the GI tract Mass balance: matching fluid input with output. input We Secrete More Fluid than We Ingest output To maintain homeostasis, the volume of fluid entering the GI tract by intake or secretion = The volume leaving the lumen. 6  Digestive processes in the small intestine: chemical digestion is completed (except for microbial activity in the large intestine) nearly all nutrient absorption occurs chyme mixed with digestive juices and slowly moved along SI moves undigested remains to the large intestine By Shrumster - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=5633706  Finger like villi in the small intestine increases surface area for absorption of nutrients Microvilli Lumen Enterocyte The anatomical structure of the wall of the small intestine has four characteristic layers. The small intestine’s surface area is increased by: Villi: Finger-like projections Crypts (invaginations) Microvilli (brush border) The increased surface area is crucial for the efficient absorption of nutrients. why do fatty acids inhibit the intestinal phase Small Intestine secretion Digestive enzymes proteases disaccharidases GI hormones - Secretin - Cholecystokinin (CCK) - Gastric inhibitory peptide (GIP) - Glucagon-like peptide-1 (GLP1) Mucus Bicarbonate Classificatio Secreted Substance Secretion Secreted By Substrate Products n Into RECAP Digestive Digestive enzymesenzymes Converts triglycerides to monoglycerides and fatty acids Nucleases Pancreas Converts DNA/RNA to nucleotides  11 https://padletuq.padlet.org/bweger/git-enzyme-1hcr7h6b08jtilym Gastric secretion and food processing is traditionally divided into 3 phases: Cephalic Gastric Intestinal Phase Phase Phase Stimulus: sight, smell, taste, or thought Presence of food in the stomach Presence of chyme in the duodenum 3. Intestinal Phase Thought of food Cephalic Phase Smell Taste Triggered by: The entry of partially digested chyme Sight from the stomach into the small intestine (duodenum). Nervus vagus Intestinal phase Vagus Mechanism: Acetylcholin hormones such as secretin, CCK, GIP and GLP1 are Liver Pepsinogen HCl HCl Secretin released, inhibiting further gastric secretion and Bile- Synthesis slowing gastric emptying. Distension Protein pH>4 p H< 4 Secretin stimulates HCO3- (bicarbonate) secretion Bile pH