physiology-15.消化与吸收1.ppt（必威体育精装版文档）.ppt

第六章消化和吸收;第一节概述;Structureofthedigestivetract;IstheabsorptivesecretorylayerlininglumenofGItract

Inplacesishighlyfoldedwithvillitoincreaseabsorptivearea

Containslymphnodules,mucus-secretinggobletcells,thinlayerofmuscle;Isathick,highlyvascularlayerofconnectivetissuewhereabsorbedmoleculesenterbloodlymphaticvessels

Containsglandsnerveplexuses(submucosalplexus)thatcarryANSactivitytomuscularismucosae;IsresponsibleforsegmentalcontractionsperistalticmovementthroughGItract

Hasaninnercircularouterlongitudinallayerofsmoothmuscle

Activityoftheselayersmovesfoodthroughtractwhilepulverizingmixingit

MyentericplexusbetweentheselayersismajornervesupplytoGItract

IncludesfibersgangliafrombothSympParasympsystems;Serosa;一、消化道平滑肌的生理特性;（一）消化道平滑肌的一般生理特性

单个单位平滑肌（内脏平滑肌）

兴奋性较骨骼肌低

较大的伸展性:能容纳性舒张，而不发生明显的压力变化和运动障碍。

一定的紧张性：经常保持微弱的持续收缩状态,维持空腔器官形态、位置及基础压力。

对刺激的特异敏感性:对电刺激和锐性刺激不敏感，对化学(ACh、酸碱)、温度和牵拉较敏感。;（二）消化道平滑肌的电生理特性

静息电位:RP较小(-50～-60mV)，K+外流、钠泵、Na+少量内流和Cl-的外流。

慢波电位:RP并不恒定地维持在一定水平上，能够在RP的基础上，自发地周期性地去极化和复极化形成缓慢的电位波动，称为慢波电位(slowwave)或基本电节律(basicelectricalrhythm)。;Slowwavesareproducedbynon-neuronalinterstitialcellsofCajal(ICC)

Conductedtosmoothmuscleviagapjunctions

Slowwavesspreadfrom1smoothmusclecelltoanotherthrugapjunctions;Whenslowwavesexceedthreshold,theytriggerAPsinsmoothmusclebyopeningV-gatedCa2+channels

InfluxofCa2+producesdepolarizationphaseofAPstimulatescontraction

RepolarizationviaK+efflux

ElectricalandContractileactivityaremodifiedbyANS(extrinsicandintrinsic)activity

AChfromParasympincreasesamplitudedurationofslowwaves

NEEpifromSympdecreaseactivityofintestines;;（三）消化道平滑肌的收缩;G;?Toniccontractions

?Propulsiveperistalsis

?Reverseperistalsis(antipropulsion)

?Massmovements(largeintestine)

?Nonpropulsivesegmentation

?Haustration-nonprop