Histological observation of the chronological changes in the constituent zones of the rabbit placenta.
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概要
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Rabbit placentae were examined histologically from Day 5 of pregnancy to Day at parturition, with special emphasis on the development and involution of each zone composing the placenta.<BR>1) The rabbit placenta was divided into three zones, placental labyrinth, junctional zone and decidua.<BR>2) The placental labyrinth appeared at Day 11 of pregnancy, following the attachment of the fetal membrane to the uterine epithelium at Day 9. This zone was structurally established at Day 17-18 of pregnancy, and continued to expand until term.<BR>3) The junctional zone appeared at the same stage as did the placental labyrinth. It was made up of large, multinucleate cells having PAS positive substances, and expanded up to Day 18-19 of pregnancy. Subsequently, it began to decrease in volume and disappeared at Day 28. Therefore, it seems that this zone plays some roles in supplying nutrition to the fetus up to the middle stages of pregnancy.<BR>4) The decidua originated from stromal cells of the mesometrial endometrium during early pre-gnancy. The decidua became divisible into zone of necrosis and zone of separation as pregnancy advanced. The zone of necrosis consisted of multinucleate cells at Day 13-14 of pregnancy. There-after, necrotic changes showing karyopycnosis and karyorrhexis gradually progressed, accompanied by an extreme enlargement of blood vessels. Extensive persistence of this zone until term seems to imply that this zone plays some important roles in maintaining interrelations between mother and fetus.<BR>5) The zone of separation appeared at Day 13-14 of pregnancy as did the zone of necrosis. In early pregnancy, this zone occupied about a half of decidua in thickness and consisted of mononuclear cells exclusively, but it became thinner toward term at which time it persisted as a 2 or 3 cell layer showing a network appearance. Examination of the afterbirth suggested that the separation of the placenta would take place at this zone.
- 日本繁殖生物学会の論文
日本繁殖生物学会 | 論文
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