蒙古绵羊早期胚胎心脏的组织发生

THE HEART HISTOGENESIS OF THE EARLY EMBRYO OF THE INNER MONGOLIA SHEEP

蒙古绵羊早期胚胎的血岛是心管及血管组织发生的原基。交配后１２～１３日龄，在胚盘两侧的胚内中胚层内，首先发生血岛，进而扩展到原肠及尿囊的脏层。在１６～１８日龄，前肠腹面的心管，由单管状变形成Ｕ字袢，进而扭转成字形。因心管中段的收缩，出现心房、心室及动脉球三个膨大。２０～３０日龄，胚长４～１５ｍｍ，在房室管内，发生前后对称的心内膜垫，将房室管分隔成左及右房室口。由于心房内，第Ⅰ第Ⅱ房间隔发生，将心房分隔成左及右心房。再由于心室内室间隔的发生，将心室分隔成左及右心室。心管传导系统的窦房结，在１６～１８日龄，发生于静脉窦右侧心外膜下，此时心管的窦房部开始搏动。本文发现，在２１～２２日龄，胚长６～８ｍｍ时，静脉窦右侧心外膜下的窦房结细胞团散在。在房间隔壁内与心内膜垫相接处，房室结的细胞团群居。还发现，绵羊胚胎的心软骨原基，发生于３０日龄，胚长１５ｍｍ时，心软骨原基位于主动脉半月瓣外围水平上与肺动脉之间。

The blood island of the Mongolia sheep embryo is the bud of the vescular and heart. After coitus for 1213d, the blood island was first formed at the two side of the entraembryonic mesoderm, and then it extended into the splanchnic mesoderm of the primitive gut and the allantois. At the age of, 1618d, the heart tube changed from a stright tube to an U-shape one. Finally twisted into a -shaped heart tube. With the middel part of the heart tube contracts, three expansions of the atrium, the ventricle and the conus were formed. At the age of 2030d, the symmetrical endocardial cushion was formed in the atriventricular canal. It devided the artiventricular canal into the right and left artiventicular foramen. As the interatrial spetum I and II was formed in the atrium, the interventricular septum was formed in the ventricle, the atrium was devided into the left and right parts, Also the ventricle was separated into two parts. At the age of 1618d, the sinoatral node was formed under the right epicardium of the sinuse venosus and began beating. At the age of 2122d, the cells of the sinoatrial node scattered under the right epicardium of the sinuse venosus. The cell mass of the atrioventricular node gathers at the area connecting the interatrial septm with the endocardial cushion. The bud of the cardiac cartilage of the sheep embryo was generated at the age of 30d, it was situated between the periphery of the aortic valve and the pulmonary artery.