The foetal blood is separated from the syncytiotrophoblast with all EXCEPT:

(Decidua-parietalis) (25, 36-Duta 6th)Decidua-vera or parietalis - the rest of the deciduas lining the uterine cavity outside the site of implantation.* Foetal blood now circulate through the villi, while maternal blood circulate through intervillous space (69-IBS- Embryology 7th)* Synocytiotrophoblast grows into the endometrium. As endometrium is eroded, some of its blood vessels are opened up, and blood from them fills the lacunar spaces {intervillous space)* Each trabeculus is initially made up entirely by syncytiotrophoblast. Now the cells of the cytotrophoblast begin to multiply and grow into each trabeculus. The trabeculus thus comes to have a central core of cytotrophoblast covered by an outer layer of syncytium. It is surrounded by maternal blood filling the lacunar space. The trabeculus is now called is primary villous.