TheDigestiveSystem

(alsocalledthegastrointestinaloralimentarycanal)

目前一頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)TheprimaryfunctionsIngestionDigestionAbsorptionEliminationIntroductionAnatomically,thedigestivesystemconsistofa30-footlong,mucousmembrane-linedtubebeginningwithmouthandendingwiththeanus目前二頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)ThedigestivesystemMouthPharynxEsophagusStomachSmallintestineLargeintestineLiverGallbladderPancreasAccessoryorgansofthedigestivesystem目前三頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前四頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)TheoralcavityTheteethThetongueThepalateChewingandswallowingTheteethareusedtocut,tearandcrushfoodintosmallerpieces.Eachtoothconsistsofpulp,cementumandenamel.Theteethareclassifiedincisors,cuspidsandmolars.Thetonguemanipulatesfoodinthemouthduringmasticationanddeglutition.Thepalatethehardplateandthesoftplate(theuvulahangingfromthesoftplate)目前五頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前六頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前七頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Thepharynxorthroat,isalongmusculartubethatservesasapassagewayforfoodfromthemouthtotheesophagusandasapasswayforairfromnosetothewindpipe.Theesophagusisalongmusculartubeextendingfromthepharynxtothestomach.Foodispropelledbyrhythmiccontractionsofmusclesinthewalloftheesophagus.Thisprocessiscalledperistalsis.目前八頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)ThestomachItiscomposedofanupperportioncalledfundus,amiddlesectionknownasthebodyandalowerportion,calledtheantrum.

Thecardiacsphincterrelaxesandcontractstomovefoodfromtheesophagusintothestomach,whereasthepyloricsphincterallowsfoodtoleavethestomachwhenitsufficientlydigested.

Asthestomachfills,therugaeunfolded,exposingthedigestiveglandsandstimulatingthemtosecretdigestiveenzymesandhydrochloricacid.Thesesubstanceshelptransformfoodpresenttoasemifluidsubstance.目前九頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前十頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Thesmallintestineistheregionofthegutwherenearlyallofthechemicaldigestionofthenutritioncomponentsoffoodtakeplace.Itdividedinto3sections:1)theduodenum2)thejejunum3)theileumInthewalloftheentiresmallintestinearemillionsofvilli.Itisthroughthecapillariesinthevillithatcompletelydigestednutrientspassintothebloodstreamandlymphvessels.目前十一頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Thelargeintestineisdividedinto4parts:cecum,colon,sigmoidcolon,andrectum.

Thececumisconnectedtothesmallintestinebytheileocecalvalve.Thecolonhas3divisions:theascendingcolon,thetransversecolon,thesigmoidcolon.Asfluidwastefromthesmallintestinepassthroughvarioussectionsofthecolon,waterisreabsorbedintobody.Therectumservesasareservoirforfeces.目前十二頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前十三頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Theliver:locatedintheupperrightquadrantofabdomen,producesbile.Besidesproducingbile,ithasseveralothervitalfunctions.Itmanufacturesbloodproteins,destorysolderythrocytesandreleasesbilirubin,removespoisons(detoxification）fromtheblood,storesandreleasesglycogenneededbythebody.目前十四頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前十五頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Thegallbladder：apear-shapedsacbehindthelowerportionoftheliver,storesbile,whichiscontinuouslysecretedbythehepaticcellsbetweenmeals.目前十六頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)目前十七頁(yè)\總數(shù)二十頁(yè)\編于二點(diǎn)Thepancreas:behindthestomach,manufacturesdigestivejuicecontainingenzyme(amylas