StructureoftheGlTractWallVeinSubmucosalplexusMesentery(plexusofMeissner)ArteryGlands insubmucosaNerveSubmucosaGlandinmucosaDuct of glandoutsidetractMyentericplexusLymphatictissueSerosa:LumenAreolarconnectivetissueEpitheliumMucosa:Muscularis:EpitheliumLaminapropriaCircularmuscleMuscularismucosaeLongitudinalmuscleFromthe mid-esophagus totheanus,thewall oftheGltracthasthegeneralstructure,included inthe epithelial layerare exocrine /endocrine cells
Structure of the GI Tract Wall From the mid-esophagus to the anus, the wall of the GI tract has the general structure, included in the epithelial layer are exocrine /endocrine cells
I. Physiological properties of gastrointestinalsmooth muscle(1)GeneralpropertiesCARDIACSKELETAL- Low excitabilitySMOOTH-High extensibilityTYPESOFMUSCLETISSUEToniccontractionwww.visiblebody.com-Autorhythmicity- High sensitivity to temperature, stretch &chemicalstimulation,but not electric stimulus
– High sensitivity to temperature, stretch & chemical stimulation, but not electric stimulus. I. Physiological properties of gastrointestinal smooth muscle (1) General properties – Low excitability – High extensibility – Tonic contraction – Autorhythmicity
Tonic contractions_ Tonic contractions are continuous instead of rhythmicaland last several minutes-to-hours- They are caused by:-Repetitive spikes- Continuous depolarization- Continuous entry of Ca?+
– Tonic contractions are continuous instead of rhythmical and last several minutes-to-hours. Tonic contractions – They are caused by: - Repetitive spikes - Continuous depolarization - Continuous entry of Ca2+
(2)Electrophysiologicalproperties(a) Resting potential:-Between-50~-60mV-lonicbasisEm (selective membrane permeability to KtNa+- K+ pump, K+, Cl, Ca2+o60Tension
– Ionic basis Em (selective membrane permeability to K+ ) Na+ - K+ pump, K+ , Cl- , Ca2+ (2) Electrophysiological properties (a) Resting potential: – Between - 50 ~ - 60 mV
(b) Slow wave (basic electrical rhythm, BER)- The spontaneous rhythmic, sub-thresholddepolarization of the cell membrane(slow wave) of the G.l. tractActionpotentialsae-Initiatedintheinterstitialcells of Cajal (ICC)Threshold(pacemakercell)60SlowwavesTime (sec)MechanicalthresholdChemicalthresholdTime (sec) 2011 Pearson Education, Inc
– The spontaneous rhythmic, sub-threshold depolarization of the cell membrane (slow wave) of the G.I. tract (b) Slow wave (basic electrical rhythm, BER) – Initiated in the interstitial cells of Cajal (ICC) (pacemaker cell) Mechanical threshold Chemical threshold