Placenta : It is physical barrier connecting the embryo from the mother womb to the uterine wall to allow nutrient uptake, waste removal etc.
Structure : In human placenta is 22‌cm in length, 2-2.5 cm in thickness, weighs 500g. It has a dark reddish-blue or crimson colour. It is discoidal in shape.Functions : This provides a large surface area for glucose and oxygen to pass from the mother to the embryo, and the developing embryo will also generate waste substances which can be removed by transferring them into the mothers blood through the placenta. Thus it provides nourishment to the embryo, helps in the excretion and provides immunity to the foetus.