The placenta is a disk like tissue formed by uterus wall as some embryonic part..( placenta is, therefore a special tissue of two individual). it is made up of finger like projection or villi of embryonal tissue, which are present on blood filled spaces if mother's tissue ( uterine wall ) .
villi, like intestinal villi provide a large surface area for exchange of material between the mother's blood and the embryo...
1.through placenta the developing embryo gets oxygen and nutrients like glucose.
2.waste generated by the embryo are transphered to mothers blood through this placenta.
3.embryo/ foetus gets some immune power against diseases from mother through this placenta.