20d、18h山羊胚胎系统形态及以后各时期体形发生

THE MORPHOLOGY OF THE 20d AND 18h GOAT EMBRYO AND THE GENESIS OF BODY-FORM IN LATE STAGE

２０ｄ、１８ｈ 山羊胎儿仍属鳃弓期，呈典型Ｃ字形，４ 对鳃弓发生，心胸突大于肝腹突，前肢芽、后肢芽均为丘状。前间、中脑泡及神经管均已产生完整；消化系统、循环系统、发育较快、各器官原基已产生；泌尿系统的后肾、生殖系统的性腺尚未发生。２０ｄ、１８ｈ ～２６ｄ 山羊胚胎为鳃弓期，４ 对鳃弓充分发育，在后期，前肢芽已由丘状变为桨状，肝腹突在后期超过心胸突，视泡、听泡、嗅窝均已发生；指蹼期：３０ｄ～３７ｄ ，虹膜产生，阴突产生，绒毛膜产生绒毛叶阜，肢芽尖端变为指状，指间有蹼膜，外观鳃裂已愈合；偶蹄期：３９ ～４７ｄ ，颈曲，背曲消失，乳腺原基初现，肢部分节，形成偶蹄；形成期与胎儿期：主要以体重增加，毛产生为特征。

About 20 days and 18 hours after coitus,the goat embryo had 4 pairs of branchial arch and became into C-shaped body.The projecting of the hart and chest was big than the belly and the liver's.The limb bud became into mound-shaped.The telencephalon,the mesencephalon the myelencephalon and the neural tube were produced.The digestive system and the circulatory system developed fast also.All the organ's buds had formed.But the metanephros and the sex gland were not producted.From 20d and 18h to 26d after coitus,the goat embryo was in the stage of branchial arch.4 pairs of branchial arch genesised.The frond limb changed its' mound-shaped into pulp board-shaped later.The projecting of the hart and chest was big than the the belly and liver's also.The optic vesicle,otic vesicle and nasal pit all genesised.The stage of thumb web was 30d-37d after coitus.The iris and genital swelling genesised.The cotyledon was produced on the surface of chorion also.The limb top was figer-shaped and there was a membrane between fingers.The branchial crack has been healed.The artiodactyla stage is during 39d-47d after coitus,the neck bent and back bent disappeared.The mammary buds is producted and the limb is node-shaped.The hoof have been formed also.The formatlon stagef and the fetus stage is 51d-91d and 96d-150d respectively.the goat embryo body weight put on fast and the its'woof has genesised in these stage.