Objective To observe the occurring time of the primary ossification center of the fetus' cranium viscerale.
目的观察胎儿面颅骨初级骨化中心出现的时间顺序。
It was concluded that the cartilage canals of fetus play great roles in formation of secondary ossification center and exist in primary secondary ossification center.
说明胎儿股骨远端次级骨化中心初始时其内存在软骨管，软骨管对次级骨化中心的形成起作用。
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