Answer
The decidua basalis helps form the maternal part of the placenta.
Work Step by Step
After the blastocyst has implanted the endometrium is called the decidua. The decidua comprises three layers : these are the decidua basais, the decidua capsularis and the decidua parietalis These names are based on the relationship of each component to the site of implantation. The decidua basalis lies between the embryo and the stratum basale of the uterus; the decidua capsularis lies over the embryo; it is the portion of the endometriun/decidua between the embryo and the uterine cavity. The decidua parietalis is the part of the decidua (endometrium) that does not become involved in the implantation process.
The decidua basalis provides glycogen and lipids for nourishment of the embryo. It is this part of the decidua that helps to form he maternal component of the placenta.
