BIOH 370 1st Edition Lecture 23 Outline of Last Lecture Digestive SystemI. Two Groups of Organsa. Alimentary Canalb. Accessory Digestive OrgansII. Functions of the Digestive SystemIII. 3 Phases of DigestionIV. Fluids Absorbed/Secreted Throughout BodyV. Layers of the GI Tract (4)VI. Enteric Nervous Systema. Organization of the Enteric Nervous SystemVII. Peritoneum and Peritoneal CavityVIII. DeglutitionIX. EsophagusX. The Stomacha. FunctionsOutline of Current Lecture Digestive System Day 2I. The StomachThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Gastric Juicesb. HCL in the StomachII. The PancreasIII. Liver and Gallbladdera. Filteringb. Functionsc. Regulation of Bile/ Pancreatic JuicesIV. Small IntestineV. Gut Associated Lymphoid TissueVI. Antigen Recognition and uptake in the GALTVII. Benefits of ProbioticsCurrent LectureDigestive System Day 2I. The Stomacha. Gastric Juices: produced by specialized stomach cellsb. HCL in the Stomach: parietal cells in gastric pit**carbonic anhydrase= catabolizes a reversible reaction= involved in alkaline tideII. The Pancreas= helps neutralize pH- Is a gland that lies posterior to the stomach- Produces enzymes that digest carbohydrates, proteins, fats, and nucleic acids- Produces sodium bicarbonate which buffers stomach acid- Empties its contents into the duodenumIII. Liver and Gallbladdera. Liver Functions:- Carbohydrate, lipid, and protein metabolism- Processing of drugs and hormones- Bilirubin excretion= byproduct of RBC breakdown- Bile salt synthesis- Storage- Phagocytosis- Vitamin D activation- The liver makes bile, important in the emulsification of fats- Liver lobuleso Hexagonal structural and functional unitso Filter and process nutrient-rich blood from GI tract (hepatic portal vein branch)o Requires blood oxygenated blood supply (hepatic artery)o Composed of plates of hepatocytes (liver cells)a. Filter bloodb. Store glycogenc. Produce bileo Bile ducts - Longitudinal central vein b. Filtering:- Liver filters all blood after leaving the GI tractc. Regulation of Bile/ Pancreatic Juices= made in liver, delivered to gallbladder- mix bile and chime to emulsify and breakdown food products- The liver makes bile, important in the emulsification of fats- The gallbladder stores bile until it is needed- Bileo Bile secretion is stimulated byo Bile salts in enterohepatic circulation o Secretin from intestinal cells exposed toHCl and fatty chymeo Gallbladder contraction is stimulated byo Cholecystokinin (CCK) from intestinal cellsexposed to proteins and fat in chymeo Vagal stimulation (minor stimulus)o CKK also causes the hepatopancreaticsphincter to relax- Pancreatic Juiceso CCK induces the secretion of enzyme-rich pancreatic juice by acinio Secretin causes secretion of bicarbonate-rich pancreatic juice by duct cellso Vagal stimulation also causes release of pancreatic juice (minor stimulus)IV. Small Intestine: Digestion, nutrient and water absorption and immune responses occur in the small intestine- Specialized cells function in digestion (carbohydrates, proteins, lipids and nucleic acids) absorption and immune surveillance and activation- S cells: secretin- CCK cells:CCK- K cells: glucose-dependent insulinotropic peptide (GIP)**Glucose can transport using secondary active transport using symportV. Gut Associated Lymphoid Tissue:- The mucosal surface of the GI tract is in direct contact with the external environment- Intestinal bacteria helps immune system encounter “good” bacteriao Susceptible to colonization by pathogens- Contains cells of innate and adaptive immune systemo Innate system: early non-specific immune responseNature Reviews Immunology3, 331-341 (2003) o Adaptive system: antigen-dependent lymphocyte effector and memory responses- Intestinal surface covers an area ~100m2- Adult human intestine ~ 1014 commensal bacteriaVI. Antigen Recognition and uptake in the GALT: (Peyer’s Patch)1. Through epithelial cells (IEC)2. DC extend dendrites through tight junctions3. Free antigen enters through Microfoldcells(M cells)4. Free antigen enters through epithelial cellsVII. Benefits of Probiotics- Can be found in yogurts- Allow for competition of beneficial bacteria- Provide colonization resistance- Provide barrier function- Increases tightness of tight junctions- Activates signals of immune system- Importance of Passing Through Birth Canal for a Babyo The birth canal provides a microflora for baby to establish important bacteria in intestine= better neonate for immune systemo The squeezing of the baby through the birth canal= empties fluids out of their lungs= better for lungso SO… baby that are not born through the birth canal are at more risk for respiratory distress and are not colonized for