IMPORTANT MODELS. Definition:The human placenta is ‘discoid’, ‘hemochorial’ and ‘deciduate’. The placenta is attached to the wall of the uterus and provides a connection between mother and fetus via the umbilical cord. Placenta is a circular disc, spongy, flaky structure, thicker at the center and thin at the corners. Placenta origin:Placenta originates from the trophoblastic layer of the fertilized ovum.It is closely linked with the mother’s circulation and helps the