Bilaminar germ Disc (2nd wk of development)
1- Blastocyst starts embedding
2- Two types could be identified :a- cytotrophoblast .
b-Syncytiotrophoblast .
- Blastocyst more deeply embedded .
- Syncytiotrophoblast shows large number of lacunae (lacunar stage).• Formation of exocoelomic cavity , surrounded by exocoelomic memb.
- Blastocyst is completely embedded .
-At embryonic pole , trophblastic lacunae connected with maternal sinusoids (uteroplacental circulation).-At extraembryonic mesoderm full the space between exocoelomic cavity and inner aspect of trophoblastic
-Uterine endometrium defect is completely healed .
-Trophoblastic lacunae present at both embryonic and abembryonic pole (uteroplacental circulation is begin ).-Primary villi could be seen .
-Secondary yolk sac is lined with endoderm completely .
Clinical notes
abnormal implantation :1- abdominal cavity (1.4%)
2-ampullary region (80%)
3-tubal implantation (12%)
4-interstitial implantation (0.2%)
5-internal os implantation (0.2%) (placenta brevia )
6-ovarian implantation (0.2%)