蒙古绵羊胚胎的原肠形成

THE GASTRULATION OF MONGOLIAN SHEEP EMBRYOS

蒙古绵羊在交配后8d 17h 10min~12d 14h 30min,胚胎发育到原肠期。胚泡呈球形,直径约266~972μm,透明带消失,滋养层由单层扁平上皮或单层立方上皮组成。交配后8d 17h 10min~9d 15h 18min,胚结呈扁圆形,直径7.0—72μm。胚结从胚泡表面微隆起,被滋养层覆盖。胚结背面的外胚层细胞呈团状,腹面分化出内胚层,胚外内胚层伸向胚结边缘的滋养层内。交配后10d 16h~10d 17h 20min,胚结背部出现泡状原羊膜腔,直径约40μm;原羊膜腔底部分化为外胚层,径约72~90μm,胚结腹面的内胚层伸向滋养层内1/2赤道处。交配后11d 16h 5min~12d 14h 30min,胚结充分发育变成圆盘状,直径约252~396μm。胚盘背部的原羊膜腔消失,外胚层暴露于胚泡表面,由复层柱状上皮组成。胚盘腹面的内胚层为扁平上皮,并沿滋养层内壁延伸,构成球形的原肠腔。

The Mongolian sheep embryo develops into gastrula from 8 days 17 hours 10 minutes to 12 days 14 hours 30 minutes after coitus.The blastocyst is spherical in shape about 266—972μm in diameter.The zona pellucida has disappeared.The trophoblast consists of simple flat epithlium or simple cuboidal epithelium.About 8 days 17 hours 10 minutes to 9 days 15 hours 18 minutes after coitus the embryonic knot becomes spheroid,about 70—72μm in diameter.The embryonic knot is slightly protruding from The surface of the blastocyst and is covered by the trophoblast,the ectodermal cells of the dorsal portion of the embryonic knot form a mass.The lower surface of the embryonic knot has differentiated into the endoderm.The extraembryonic endoderm extends to the inner surface of the trophoblast from the periphery of the embryoblast.About 10 days 16 hours to 10 days 17 hours 20 minutes after coitus,in the dorsal portion of the embryonic knot forms a vesicle which is known as the primitive amniotic cavity about 40μm in diameter.The bottom of the primitive amniotic cavity has differentiated into the ectoderm,about 72—90μm in diameter.The endoderm of the lower surface of the embryonic knot continues to develop along the inner surface of the trophoblast to the equator.The developmental process of the primitve amniotic cavity of Mongolian sheep embryos is different from rabbit、guinea pig and human embryos,but it is similar to the mole embryos.About 11 days 16 hours 5 minutes to 12 days 14 hours 30 minutes after coitus,the embryonic knot becomes discal in shape and is fully developed,about 252—396μm in diameter.The primitive amniotic cavity of the dorsal portion of the embryonic disc has disappeared.The ecitoderm is exposed to the surface of the blastocyst,it consists of stratified columnar epthelium.The endoderm of the lower surface of the embryonic disc consists of the simple flat epithelium,it forms a spherical primitive gut cavity along the inner surface of the trophoblbst.