TheNormalHeartandHowItWorks
Thenormalheartisastrong,hard-workingpumpmadeofmuscletissue.It'saboutthesizeofaperson'sfist.
Thehearthasfourchambers.Theuppertwochambersaretheatria,andthelowertwoaretheventricles(FigureA).Thechambersareseparatedbyawalloftissuecalledtheseptum.Bloodispumpedthroughthechambers,aidedbyfourheartvalves.Thevalvesopenandclosetoletthebloodflowinonlyonedirection.
Congenitaldefectsmayinvolveavalve,achamber,theseptum,anarteryorbloodflowissues.
Thefourheartvalvesare:
1.thetricuspidvalve,locatedbetweentherightatriumandtherightventricle;
2.thepulmonary(pulmonic)valve,betweentherightventricleandthepulmonaryartery;
3.themitralvalve,betweentheleftatriumandleftventricle;and
4.theaorticvalve,betweentheleftventricleandtheaorta.
Eachvalvehasasetof"flaps"(alsocalledleafletsorcusps).Themitralvalvenormallyhastwoflaps;theothershavethree.
Healthyheartbloodflowpatterns
Thenormalbloodflowisacyclethatflowslikethis;body-heart-lungs-heart-body.Nextwewilllookateachstep.
Fromthebodytotheheart.FigureBbelowshowsdarkbluishblood,lowinoxygen,flowingbacktotheheartaftercirculatingthroughthebody.Itreturnstotheheartthroughveinsandenterstherightatrium.Thischamberemptiesbloodthroughthetricuspidvalve(B)intotherightventricle.
TheNormalHeartandHowItWorks
Fromthehearttothelungs
Therightventriclepumpsthebloodunderlowpressurethroughthepulmonaryvalveintothepulmonaryartery.Fromtherethebloodgoestothelungswhereitgetsfreshoxygen(C).
Fromthelungstotheheart
Afterthebloodisrefreshedwithoxygen,it'sbrightred.Thenitreturnstotheleftheartthroughthepulmonaryveinstotheleftatrium.Fromthereitpassesthroughthemitralvalve(D)andenterstheleftventricle.
Fromthehearttothebody
Theleftventriclepumpstheredoxygen-richbloodoutthroughtheaorticvalveintotheaorta(E).Theaortatakesbloodtothebody'sgeneralcirculation.Thebloodpressureintheleftventricleisthesameasthepressuremeasuredinthearm.