Study On Embryo And Fetal Morphology Development During Early Pregnancy In Yaks

The present study was carried out by use of anatomic and histological methods to investigate the development of the outer-formation and the time of different outer-organs in the early pregnant periods in yaks. The development of reproductive glands was also observed particularly. The following results were obtained.(1) A transparent embryonic bursa is found on the 18th day of gestation, and it expands into the other side of uterus horn on 20th day. A embryo does not discovered until 28th day of gestation.(2) The fore-limb bud is observed to form on 28th day of gestation, and the hind-limb bud on 30th day. The coelom divides into thorax and celiac part on 32th day and the fetal period came on 40th day.(3) The rhombencephalon does not observed until on the 30th day of gestation and the rhombencephalon angle is about 5 degrees on the 45th day.(4) The eyes of the embryo appeare on the 28th day of gestation. It could be observed clearly with a diameter of approximately 0.5 cm on the 34th day.(5) The sex differentiation in male embryo occurrs on 36th -40th day of gestation.(6) The development of embryos turns into a milestone stage after 36 days of gestation. The size and weight of them increase extremely henceforth.