Tam W H, Burgess S M
J Anat. 1977 Jul;123(Pt 3):601-14.
The placental disc and the yolk sac endoderm of intact guinea-pigs from day 14 of gestation to term, and of ovariectomized and fetectomized animals at 35 days of pregnancy, were observed by histological means. The chorionic giant cells were the first to attain maximal development (between days 17-35) and they had begun to degenerate by day 40. The spongy zone syncytiotrophoblast was well established and vascularized by day 18, and the maximal size of the zone was maintained between days 30 and 64. The spongy zone then dwindled in size just before parturition. Labyrinthine tissue appeared on day 18, but rapid growth and complete vascularization was not attained until as late as day 40. However, its continued increase in size almost up to term closely paralleled the growth of the fetus. If the placenta secretes progesterone from day 18 to parturition, the spongy zone is the only tissue sufficiently well established to carry out this activity throughout this period. The compensatory hypertrophy of the spongy zone syncytiotrophoblast in 35 day pregnant animals after ovariectomy and fetectomy supports the hypothesis that the spongy tissue secretes progesterone.
采用组织学方法观察了妊娠14天至足月的完整豚鼠以及妊娠35天时去卵巢和摘除胎儿的动物的胎盘盘和卵黄囊内胚层。绒毛膜巨细胞最先达到最大发育程度（在第17 - 35天之间），到第40天时开始退化。海绵状带合体滋养层在第18天时已发育良好并形成血管，该区域的最大尺寸在第30天至64天之间保持稳定。然后，海绵状带在分娩前尺寸逐渐缩小。迷路组织在第18天出现，但直到第40天才实现快速生长和完全血管化。然而，其大小几乎持续增加直至足月，这与胎儿的生长密切平行。如果胎盘从第18天到分娩都分泌孕酮，那么海绵状带是在此期间唯一充分发育到能够进行此项活动的组织。去卵巢和摘除胎儿后妊娠35天的动物中，海绵状带合体滋养层的代偿性肥大支持了海绵状组织分泌孕酮这一假说。
