chapter23 digestivepart1marieb

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  • 1. Digestive System, Part 1Objectives:Discuss the general functions andanatomy of the digestive tract,including accessory structures.First, an overview of the tubular natureof the digestive system.Describe the individual organs of thesystem, including a discussion of thegross and microscopic anatomy.Developed by John Gallagher, MS, DVM

2. Digestive System Overview AKA: Digestive Tract Alimentary Tract or Canal GI tract GutMuscular, hollow tube,from the lips to the anus+Various accessory organs 3. Digestive System OverviewThe function of the system as a whole isprocessing food in such a way that nutrientscan be absorbed and residues eliminated.Individual partsfunction in: Ingestion Propulsion Mechanical digestion and segmentation Chemical and enzymatic digestion Secretion Absorption Compaction Excretion and elimination (defecation) 4. MembranesPeritoneum - generic serous membrane inabdominal cavityParietal and Visceral PeritoneumRetroperitoneal vs. (intra)peritonealMesenteries - double sheets of peritoneum, surrounding andsuspending portions of the digestive organs Greater omentum - "fatty apron", hangs anteriorly fromFig. 22.6stomach; double layer encloses fat Lesser omentum - between stomach and liver Mesentery proper - suspends and wraps the small intestine Mesocolon - suspends and wraps the colon, parts are transverse mesocolon sigmoid mesocolon 5. GeneralOrganization 6. Structure of Small Intestinal WallPlicae circulares circular pleats around the interior of the smallintestineVilli minute finger-like projections, contain capillaries & lactealsMicrovilli sub-microscopic size, projections on single cells Function of all three? Crypts at bottom of villiCell regeneration (mitosis) Glandsmucus, enzymes 7. Smooth Muscle, areview One nucleus Nonstriated Actin and myosin present Slow, sustainedcontraction Communication Varicosities Gap junctions 8. Histological OrganizationTube made up of fourlayers.1. Mucosa2. Submucosa3. Muscularis externa4. Serosa = VisceralPeritoneumModifications along itslength as needed. 9. The 4 Layers of the Gut1) MucosaEpithelium - usually simple columnar epithelium with goblet cells;may be stratified squamous if protection needed, e.g., esophagusLamina propria areolar connective tissue deep to epitheliumMuscularis mucosae -produces folds - plicae (small intestine) or Fig 23.7rugae (stomach) 10. The 4 Layers ofthe Gut2) Submucosa made up of loose connective tissuecontains submucosal plexus and blood vessels Fig 23.7 11. The 4 Layers ofthe Gut3) Muscularis externa smooth muscle, usually two layers(controlled by the myenteric plexus; source of peristalsis )- inner layer: circular outer layer: longitudinal Fig 23.7 12. The 4 Layers of the Gut4) Serosavisceral layer of mesentery (contiguouswith the peritoneum) or adventitiadepending on locationFig 23.7 13. Repetitio estmater studiorum 14. OralCavity AKA buccal cavity or mouth - lined with oral mucosa (type of epithelium ?) Lips = labia Labial frenulum Hard and soft palates - form roof of mouth Tongue - skeletal muscle Lingual frenulum Salivary glands - three pairs Teeth Fauces = opening to pharynx 15. Types and Numbers of TeethDental successionDeciduous (1o, baby, milk)teeth - 20, replaced byPermanent teeth - 32 teeth 16. Structure of TeethFig 23.14Crown - exposed surface of toothNeck - boundary between root and crownEnamel - outer surfaceDentin bone-like, but noncellularPulp cavity - hollow with blood vessels and nervesRoot canal - canal length of rootGingival sulcus - where gum and tooth meetPeriodontal Ligament 17. Three pairs of Salivary Glands1-1.5 L / day fordigestion (?)lubrication (swallowing) moistening(tasting) Parotid lateral side of face,anterior to ear, drain by parotidduct to vestibule near 2ndupper molar Submandibular medialsurface of mandible drainnear lingual frenulum drainposterior to lower molars Sublingual in floor of mouth -drain near lingual frenulum 18. MumpsSwollen, painful parotid salivary glands (parotitis) on one or both sides ofthe faceEtiology: Mumps virus (Myxovirus)Fever and sometimes orchitis, pancreatitis etc.About 1/3 of infected people do not show symptomsEffective vaccine (MMR) since 1967 19. Esophagus Lined with noncornifiedstratified squamous epithelium Food boluses propelled byperistalsis of both skeletal andsmooth muscle (gravity, too) Hiatus; lower esophagealsphincter GERD 20. StomachoCardiac Sphincter (?)oCardiaoFundusoBodyoPylorusoPyloric sphincteroGreaterand LesserCurvaturesoGreater Omentum 21. StomachRugae or RugalFoldsPylorusPyloric sphincter 22. Circulation 23. Histology of StomachType of epithelium lining stomach?Gastric pits shallow pits, external half rapidlyreproduces for replacementGastric glands deep in lamina propria, 3 types ofcells1. Parietal cells (produce HCl and intrinsic factor B12)2. Chief cells (produce pepsinogen)3. Enteroendocrine cells G cells (severalhormones including gastrin which stimulates bothparietal and chief cells) 24. Ulcers Mucosal erosion of stomach orduodenum GERD NSAIDs Helicobacter pylori Stress?? Dx byesophagogastroduodenoscopy h?v=hm1nEP HxJ0E 25. Review:


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