摘要
蒙古绵羊胚胎发育到１７ｄ１７ｈ 第Ⅰ对鳃弓动脉发生，到２１ 日龄第Ⅱ～Ⅵ对鳃弓动脉相继发生，其中第Ⅰ、Ⅱ及Ⅴ对鳃弓动脉又退化，仅第Ⅲ、Ⅳ及Ⅵ对鳃弓动脉发育成永久性动脉。从２１ ～２４ 日龄，动脉干内的干嵴发生并吻合，因此动脉干被分隔成主动脉及肺动脉。在此同时，动脉球内的球嵴也吻合分隔成两个通道与上述动脉相通。胚胎的肺芽开始发生于２０ 日龄，到２２ 日龄肺动脉已向肺芽发出分支，到２４ 日龄肺静脉已从肺芽伸入左心房。从１８ ～２０ 日龄，第Ⅲ对鳃弓动脉背段分化成颈内动脉，腹段分化成颈外动脉。从２０ ～２１ 日龄，锁骨下动脉从两侧对称的背主动脉发生，随着右侧背主动脉退化，右臂头动脉前移与左锁骨下动脉合并成臂头动脉总干。从１３ ～２４ 日龄，肠系膜前动脉、腹腔动脉和肠系膜后动脉相继发生。胚胎发育到２０ ～２４ 日龄，背主动脉后端中央发生中荐动脉，两侧分出脐动脉分布于尿囊，在脐动脉根部发出髂外动脉分布于后肢芽。
At the age of 17-21d of embryo,the first、second and fifth pairs of aortic arches degenerated.only the third、fourth and sixth pairs of aortic arches grew into permanent aorta.\;At the age of 20d the lung bud began to grow.At the age of 22d the pulmonary artery had branched into the lung bug.At the age of 24d the pulmonary vein came into the left atrium from the lung bud.\;At the age of 18-20d the dorsal part of the third aortic arches becames the internal carotid artery and the abdominal part becames the external carotid artery. At the age of 18-21d the subclavian arteries generated from the symmetrical dorsal aorta with the degenerating of the right dorsal aoeta,the right brachiocenhalic arteries moved forward to the left aortic arches and combined into common truncus of brachiocephalic artery. At the age of 13-24d the phalomesenteric artery was divided into superior mensenteric artery、the coeliac artery and the inferior mensenteric arteries. At the age of 20-21d the middle sacral artery developed from the centre of dorsal aorta's behind.The umblical arteries developed from the two sides of dorsal aorta and distrituted to allantois. The externaliliac arteries developed from the root of unblical artery and distributed to hind limb bud.
