Development of Inf. venacavaand Pulmonary veinAnup PandeyDept. of Human AnatomyB.P. Koirala Institute of Health SciencesDharan Nepal
Cardinal veins• Anterior cardinal veins:drains the cephalic part ofthe embryo, including thebrain.• Posterior cardinal veins:drain the rest of the part ofthe embryo.At their cranial ends theseveins join the ant cardinalveins to form the commoncardinal vein.
• Near their caudal endthey receive veins of thelower limb bud – externaliliac vein and of the pelvis– internal iliac veins.• The caudal ends of thetwo posterior cardinalveins becomeinterconnected by atransverse anastomosis.
• Subcardinal veins: formedin relation to themesonephros whichcommunicate cranially andcaudally with the posteriorcardinal veins.• The subcardinals receivethe veins from thedeveloping kidneys.
• At the level of the renalveins the two subcardinalveins becomeinterconnected by atransverse inter-subcardinalanastomosis.
• The cranial part of the rtsubcardinal veins alsoestablishes an anastomosiswith the right hepatocardiacchannel.
• Supracardinal veinsCommunicate cranially andcaudally with the posteriorcardinal veins and also withthe subcardinal veins thr thesubcardinal-supracardinalanastomoses.
• Many parts of thislongitudinal venouschannels disappear• The veins that remain giverise to the inferior venacava, renal vein, veins ofgonads and the suprarenalveins.
• Inferior venacava:derived from:1. Lowest part of the rtposterior cardinal vein andthe anastomosis betn twoposterior cardinal veins.2. Lowest part of thert.supracardinal vein3. Rt. Supracardinal-subcardinal anastomosis.4. Right subcardinal vein5. Subcardinal-hepatocardiacanastomosis.6. Rt. Hepatocardiac channel.
• Rt common iliac vein:derived from the mostcaudal part of the rt.posterior cardinal vein.• Left common iliac vein:from the anastomosis betntwo posterior cardinal veins.• Rt renal vein: derived frommesonephric vein thatdrains into the rtsubcardinal vein.
• Left renal vein:derived froma) Mesonephric veinthat drains into leftsubcardinal veinb) Small part of the leftsubcardinal veinc) Inter-subcardinalanastomosis.
• Suprarenal vein: derivedfrom the remnants of theparts of subcardinal veinsabove the inter-subcardinalanastomosis.
• The termination of the rtsuprarenal vein in the IVCand that of the leftsuprarenal vein in the leftrenal vein is because oftheir developmental origin.• Gonadal veins: derivedfrom the remnants of theparts of subcardinal veinsbelow the inter-subcardinalanastomosis.
Clinical correlates• Double inferior venacava:generally the inf venacavais double only below thelevel of renal veins.a) Both channels may bepresent on the right sidedue to persistence ofboth the subcardinal andsupracardinal veins belowthe level of kidneys.b) There may be additionalchannel on the left side.
• Left inf venacava:The infrarenal partof the venacavamay be present onthe left side only.
• Azygos continuation ofinf venacava:The hepatic segment ofthe inf venacava maybe absent.In such case, upperpart of the inf venacavafollows the course ofthe azygos vein andopens into the superiorvenacava.
• Pre ureteric venacava:Inf venacava normally liesposterior to the right ureter.If it is anterior to the rt. ureter,it may hook around the left sideof the venacava.This anomaly is caused whenthe infra renal part of thevenacava develops from thesubcardinal vein instead ofsupracardinal vein.
Pulmonary veins• The pulmonary veins arethose structures that formindependently, rather thanfrom the portions of thecardinal venous system.• When the septum primum isjust beginning to form, asingle pulmonary vein opensinto the left atrium.
• The single pulmonary vein now divides intort. and left branch.• Each of these veins again bifurcates to drainthe corresponding lung bud.
• Gradually the parts ofthe pulmonary veinsnearest to the leftatrium are absorbedinto the atrium.• As a result fourseparate veins, twofrom each side, cometo open into the leftatrium.
Summary• Formation of Inf venacava:1. Lowest part of the rtposterior cardinal vein andthe anastomosis betn twoposterior cardinal veins.2. Lowest part of thert.supracardinal vein3. Rt. Supracardinal-subcardinal anastomosis.4. Right subcardinal vein5. Subcardinal-hepatocardiacanastomosis.6. Rt. Hepatocardiac channel.
• How theSuprarenal veinformed??• How the Gonadalveins formed??• Nature oftermination ofthe veins on thert and left side??
• How the formation of pulmonary veinsoccurs??