蒙古绵羊早期胚胎静脉系统的组织发生

HISTOGENESIS OF THE VENOUS SYSTEM OF THE EARLY EMBRYO OF MONGOLIA SHEEP

蒙古绵羊胚胎发育到１７ｄ、１７ｈ ，心房两侧有３ 对静脉原基发生，包括总主静脉，脐静脉及脐肠系膜静脉。胚胎发育到３０ｄ 龄，左总主静脉右移分化成冠状静脉。右总主静脉则分化成前腔静脉。３０ｄ 龄以后，左及右前主静脉间发生吻合，称左臂头静脉。左及右臂头静脉合并后汇总于前腔静脉。胚胎发育到２９ｄ 龄，后主静脉前段及中段退化，后段分化成总髂静脉。脐肠系膜静脉发生于卵黄静脉。胚胎发育到２０ ～３０ｄ 龄，在中肾的腹内侧发生左及右下主静脉间吻合。此吻合组成后腔静脉的肝部。在２４ｄ 龄以后，中肾背侧发生上主静脉。上主静脉接受总髂静脉，经上及下主静脉间吻合，再经腔皱襞汇入后腔静脉。

When the embryo was at the age of 17 days 17 hours( E17d17h),there were 3 pairs of the venous rudiments behind the cardiac tube.They were the Common Cardinal Veins, the umbilical veins and the Omphalomesenteric veins. At E30d,the left common cardinal vein moved toward the right and differentiated into coronary vein.After E30d,the left and right brachiocephalic veins were combined to the superior vena cava.At E29d,the anterior and mesial regions of the posterior cardinal vein began to degenerate.The Omphalomesenteric veins developed from the yolksac vein, At E20-30d, the left and right subcardinal anastomosis develops at the vetral interior of the mesonephros. This anastomosis formed along the caval plica the hepatic regin of the inferior vena cava. After E24d. The supracardinal veins developed at the back of the mesonephros,That acceped the blood from the common iliac vein and passed by the supracardina land subcardinal anastomosis and the caval plica. Finally they combined into the inferior vena cava.