Lecture 2: Introduction to GI Physiology Part 1 PDF

Lecture 2 Introduction to GI Physiology Part 1 1 Click to add footer  LOs Today List the layers of the tubular GI tract Contrast the roles of the autonomic nervous system vs. the enteric nervous system in GI motility Name the componen...

Lecture 2 Introduction to GI Physiology Part 1 1 Click to add footer  LOs Today List the layers of the tubular GI tract Contrast the roles of the autonomic nervous system vs. the enteric nervous system in GI motility Name the components of the enteric nervous system List the main components of the intestinal barrier Give examples of how each component of the intestinal mucosa functions to serve as a barrier Use appropriate directional terminology in regards to the GI tract Relate aspects of the GI microbiota to function of GI mucosal physiology 2 Click to add footer  LOs for Later Application Examples Describe the normal functions (motility, secretion, digestion & absorption) of the stomach Compare and contrast the characteristics of gastric motility with or without the presence of food. Describe the types and functions of the brush border enzymes. Sketch the central lacteal and its describe its function in digestion. Compare and contrast the patterns of motility in the small intestine during the digestive and inter-digestive phases Describe the actions of salivary, pancreatic and microvilli enzymes in carbohydrate/protein digestion. Compare the factors that regulate movement of the contents of the ileum into the large intestine. Explain the mixing movements of the large intestine and the roles of the haustra. Describe the propulsive movements of the large intestine and the factors that affect them. Explain the beneficial and harmful effects of intestinal microbiota on the host. Explain the absorptive functions of the large intestine. 3 Click to add footer  Today Functional anatomy Outside in 4 Click to add footer  Functional Anatomy Tubular GI tract terminology Eii Ñ ir 5 Click to add footer  Functional Anatomy Mucosa Epithelium that lines the lumen of the GI tract Submucosa Underlying connective tissue Collagen with blood vessels and nerves Muscularis Smooth muscle that produces wave-like contractions (peristalsis) Serosa Connective tissue; outermost covering 6 Click to add footer  Functional Anatomy i Blood supply Innervation rififfe 7 Click to add footer  a Functional Anatomy 1 07 Layers Onion Serosa Muscularis Outer longitudinal Inner circular 8 Click to add footer  Functional Anatomy Layers Onion Serosa Muscularis Outer longitudinal Inner circular 9 Click to add footer  Functional Anatomy Muscularis function? Peristalsis - progression of coordinated contractions and relaxations of the smooth muscles of the GI tract to propel food. Other motility patterns Tomorrow 10 Click to add footer  Enteric Nervous System (ENS) Independent and intrinsic to the GI tract Controls nearly all aspects of GI function Motility Secretions Blood flow Second brain Can operate independently of CNS Complex # of neurons = # of neurons in spinal cord 11 Click to add footer  Enteric Nervous System Two interconnected systems of ganglia Myenteric (Auerbach) Between muscle layers Larger system more complex Submucosal (Meissner) Submucosa 12 Click to add footer  Functional Anatomy Enteric nervous system CAN operate independently from CNS But normally does receive input 13 Click to add footer  Autonomic Nervous System What are the two main components of the ANS? 14 Click to add footer  Enteric Nervous System Parasympathetic innervation Vagus nerve Terminal colon pelvic nerve via sacral spinal cord Ach is the NT Rest, relax, digest Sympathetic innervation Postganglionic fibers Follow splanchnic nerves and vasculature Norepinephrine is the NT All energy goes to fight or flight 15 Click to add footer  Motility Schematic showing that the ENS does everything. The 2 components are = Efferent interconnected and they communicate with CNS = Afferent = Interneuron Mechanoreceptors Chemoreceptors Glandular secretions Motility Direction, intensity, Hormones from GI endocrine cells frequency, etc Blood flow vascular smooth muscle 16 Click to add footer  Gut Brain Endocrine Axis Mention for future discussions Enteric Nervous System GI Endocrine System GI Motility and secretory functions 17 Click to add footer  Motility Sphincters - a ring of muscle surrounding and serving to guard or close an opening or tube GI sphincters Upper esophageal sphincter Closed Open 18 Click to add footer Pollard et al 2019  Motility Sphincters - a ring of muscle surrounding and serving to guard or close an opening or tube GI sphincters Upper esophageal sphincter Lower esophageal sphincter 19 Click to add footer Ullal et al 2022  Motility Sphincters - a ring of muscle surrounding and serving to guard or close an opening or tube GI sphincters Upper esophageal sphincter Lower esophageal sphincter Pyloric sphincter 20 Click to add footer  Motility Sphincters - a ring of muscle surrounding and serving to guard or close an opening or tube GI sphincters Upper esophageal sphincter Lower esophageal sphincter Pyloric sphincter Ileocecal valve Dogs and cats The ileocolic junction (ICJ) Ileum communicates with the ascending colon forming a tube that is joined by the caecum to one side 21 Click to add footer  Motility Sphincters - a ring of muscle surrounding and serving to guard or close an opening or tube GI sphincters Upper esophageal sphincter Lower esophageal sphincter Pyloric sphincter Ileocecal valve Dogs and cats The ileocolic junction (ICJ) Ileum communicates with the ascending colon forming a tube that is joined by the cecum to one side Anal sphincters Internal sphincter ENS and ANS External sphincter Voluntary control pudendal nerve 22 Click to add footer  Questions? 23 Click to add footer  Intestinal Mucosa 24 Click to add footer  Intestinal Barrier 25 Click to add footer  Intestinal Barrier Mucosa 26 Click to add footer 27 Click to add footer  Intestinal Barrier Intestinal mucosa Epithelium Cells Lamina propria Loose collagen Immune cell rich Muscularis mucosa Thin layer of smooth muscle Then the submucosa etc 28 Click to add footer  Mucosal Structure 29 Click to add footer  Lumen 30 Click to add footer  Mucosal Structure Crypts vs villi SI vs LI Both have crypts Hills and valleys SI has villi Towers on top of the hills Dr. Thomas Caceci 31 Click to add footer  Mucosal Structure Intestinal stem cells in the crypt Migrate toward lumen Differentiate Cells migrate, die, slough Terminal differentiation Die Slough Cells migrate and 3-5 days differentiate into other types Stem cells in crypt 32 Click to add footer  Mucosal Structure Intestinal epithelial cells Simple columnar Absorptive epithelial cells Lumen Enterocytes Colonocytes Other types of epithelial cells Goblet cells Paneth cells Stem cells Neuroendocrine Enteroendocrine Many others 33 Click to add footer  Layers of Mucosal Barrier From lumen to tissue Microbiota Mucus Antimicrobial Peptides And immunoglobulins Epithelial cells Tight junctions between cells Lamina Propria Immune cells 34 Click to add footer  Intestinal Barrier Epithelial cells Tight junctions between cells Barrier Controlled transport Absorption Enzymes 35 Click to add footer  Intestinal Barrier Mucus layer(s) Produced by Goblet cells Physical barrier Food for beneficial bacteria 36 Click to add footer  Intestinal Barrier Antimicrobial peptides Made by Paneth cells In the crypts 37 Click to add footer  Intestinal Barrier Lamina propria Immune cell rich Last line of defense 38 Click to add footer  Questions 39 Click to add footer  Microbiota 40 Click to add footer  Mucosal Structure Mucosal Surface Relative hypoxia PO2 Partial pressure of oxygen Normal ~ 90 100 mmHg Counter current blood flow Needed for microbes in lumen! This is a GOOD thing Hewawasam et al 2020 41 Click to add footer  Intestinal Barrier 8,045,311,447 42 Click to add footer  Gut Microbiota Population Collection of micro-organisms bacteria, fungi, viruses, and archaea Location # of species? Horses = ~1000 species Dogs/people = ~ 750 species Ruminants? 1010-1012 in rumen Feces similar to dogs Number of species similar to dogs 43 Click to add footer  Microbiota Microbiota Organisms in a defined environment Microbiome Organisms and their output Proteins, metabolites, etc Metagenome All of the genes present in a microbiota 44 Click to add footer  Microbiome Genes People = ~22,250 Human gut microbiota = 3,300,000 150:1 Dog = ~22,250 Dog gut microbiota = 1,200,000 50:1 Horse = ~22,250 Horse gut microbiota = 25,000,000 1100:1 Metagenome Metabolome (iHMP) (Coelho 2018) (Mach et al 2022) 45 Click to add footer  Gut Microbiota Culture? Fastidious Anaerobic Specific requirements 20-60% not cultivable Traditional techniques Newer technologies 46 Click to add footer  Gut Microbiota Differences along GI tract 47 Click to add footer Microbiology. 166. 10.1099/mic.0.000853.  Gut Microbiota Function? Everything Part of intestinal barrier Blue diamonds = bacteria Competition with pathogens GI Motility Serotonin and other NTs are made by some bacteria 48 Click to add footer  Questions 49 Click to add footer