Lacunar networks are developing within the syncytiotriophaoblas layer and the blood has entered these spaces.
The blastocyst has completely implanted into the endometrium and has formed a bilaminar disc which consist of epiblast and hypoblast.
The primordium of the chorionic cavity the so-called coelomic spaces develop in the extraembryonic mesoderm. Fusion of these spaces gives rise to the chorionic cavity.