The fetus is enclosed by a number of membranes and is connected to the uterine wall by the zonary placenta. This structure provides an indirect connection between the mother and fetus. In the capillary beds of the placenta the maternal and fetal circulatory systems are in proximity and nutrients, oxygen, and waste products can be exchanged. In the region of the placenta the chorioallantoic membranes fuse with the placenta and form connections to the walls of the uterine horn. Lying under the chorioallantoic membrane is the amniotic membrane. This membrane directly surrounds the embryo and produces the amniotic fluid in which the fetus is cushioned.