Within the developing fetus. The organ that is involved in exchanging gas between the mother and the fetus is called the placenta. Now, the placenta has other functions as well, but in this lecture we're going to focus primarily on its function in gas exchange. So let's begin by actually looking at the structure of our placenta. So this is a diagram of the placement placenta. So we have the umbilical cord shown here that contains two types of blood vessels.