Where and how nutrients enter the developing embryo.

If we are talking about mammals, then we mean the placenta as a source of nutrients for the embryo. After the fusion of gametes, a zygote is formed, which is implanted into the lining of the uterus and feeds directly on the mother’s blood. A month later, the placenta begins to form. It is a system of membranes that form a barrier between mother and fetus. The placenta filters the mother’s blood, selects nutrients from it, which are delivered to the fetus through the umbilical cord.