- Email: [email protected]
The veins of the descending and sigmoid colons, rectum and anal canal
COLOR ILLUSTRATIONS
279
THE VEINS OF THE DESCENDING AND SIGMOID COLONS, RECTUM AND ANAL CANAL
T
HE venous system of the Iower rectum comprises two pIexuses, the interna or superior hemorrhoida pIexus (I .H.P.), and the externa1 or inferior hemorrhoida pIexus, (E.H.P.). The interna or superior hemorrhoidal pIexus consists of a network of smaI1 veins situated in the submucosa above the anorecta1 line. In the iIIustrations, a pane1 of mucosa has been removed from the posterior recta1 waI1 to show this network. On the anterior waI1, the muscuIar Iayer has been cut away at a higher IeveI than has the mucosa in order to demonstrate the manner in which the smaI1 veins of this pIexus course upward. At about the middIe of the rectum, the veins penetrate the muscuIar Iayer. They continue upward on the outer surface of this muscuIar Iayer, uniting with one another to form the right and Ieft branches of the Superior Hemorrhoida Vein (R.S.V.) (L.S.V.). These branches course upward on the posterior aspect of the rectum and unite to form the Superior Hemorrhoida Vein proper (S.H.V.). This in turn drains by way of the Inferior Mesenteric Vein (I.M.V.) and SpIenic Vein (S.V.) to the PortaI Vein (P.V.) and thus to the Iiver. The ExternaI or Inferior Hemorrhoida pIexus is Iocated outside the muscuIar Iayer of the Iower rectum and ana cana1. It is drained on each side by two veins, the MiddIe HemorrhoidaI, (M.H.V.) and the Inferior Hemorrhoida (I.H.V.). The Inferior Hemorrhoida vein is a tributary of the InternaI Pudendal Vein (I.P.V.) which in turn enters the respective Hypogastric Vein (H.V.). The Superior Hemorrhoida Vein drains directIy into the Hypogastric. The Hypogastric Vein on each side joins the ExternaI IIiac to form the Common IIiac Vein (C.I.V.) and the two common IIiacs unite with each other to form the Inferior Vena Cava (I.V.C.) Ieading to the heart. It is thus obvious that the InternaI or Superior Hemorrhoidal pIexus drains by way of the “PortaI CircuIation” whiIe the External or Inferior pIexus drains by way of the “CavaI CircuIation.” The two pIexuses, however, anastomose with each other (An.) and this anastomosis is of considerabIe significance as it forms a juncture point of the two great venous systems--the cava1 and the porta1. The bIood from the Sigmoid CoIon and Descending CoIon is drained by way of the Sigmoid Veins (S.V.) and the Left CoIic Vein (L.C.V.) into the porta circulation.
279
THE VEINS OF THE DESCENDING AND SIGMOID COLONS, RECTUM AND ANAL CANAL
T
HE venous system of the Iower rectum comprises two pIexuses, the interna or superior hemorrhoida pIexus (I .H.P.), and the externa1 or inferior hemorrhoida pIexus, (E.H.P.). The interna or superior hemorrhoidal pIexus consists of a network of smaI1 veins situated in the submucosa above the anorecta1 line. In the iIIustrations, a pane1 of mucosa has been removed from the posterior recta1 waI1 to show this network. On the anterior waI1, the muscuIar Iayer has been cut away at a higher IeveI than has the mucosa in order to demonstrate the manner in which the smaI1 veins of this pIexus course upward. At about the middIe of the rectum, the veins penetrate the muscuIar Iayer. They continue upward on the outer surface of this muscuIar Iayer, uniting with one another to form the right and Ieft branches of the Superior Hemorrhoida Vein (R.S.V.) (L.S.V.). These branches course upward on the posterior aspect of the rectum and unite to form the Superior Hemorrhoida Vein proper (S.H.V.). This in turn drains by way of the Inferior Mesenteric Vein (I.M.V.) and SpIenic Vein (S.V.) to the PortaI Vein (P.V.) and thus to the Iiver. The ExternaI or Inferior Hemorrhoida pIexus is Iocated outside the muscuIar Iayer of the Iower rectum and ana cana1. It is drained on each side by two veins, the MiddIe HemorrhoidaI, (M.H.V.) and the Inferior Hemorrhoida (I.H.V.). The Inferior Hemorrhoida vein is a tributary of the InternaI Pudendal Vein (I.P.V.) which in turn enters the respective Hypogastric Vein (H.V.). The Superior Hemorrhoida Vein drains directIy into the Hypogastric. The Hypogastric Vein on each side joins the ExternaI IIiac to form the Common IIiac Vein (C.I.V.) and the two common IIiacs unite with each other to form the Inferior Vena Cava (I.V.C.) Ieading to the heart. It is thus obvious that the InternaI or Superior Hemorrhoidal pIexus drains by way of the “PortaI CircuIation” whiIe the External or Inferior pIexus drains by way of the “CavaI CircuIation.” The two pIexuses, however, anastomose with each other (An.) and this anastomosis is of considerabIe significance as it forms a juncture point of the two great venous systems--the cava1 and the porta1. The bIood from the Sigmoid CoIon and Descending CoIon is drained by way of the Sigmoid Veins (S.V.) and the Left CoIic Vein (L.C.V.) into the porta circulation.