Umbilical cord from and contains remnants of the yolk sac and allantois. It forms by the fifth week of development, replacing the yolk sac as the source of nutrients for the embryo. The cord is not directly connected to the mother's circulatory system, but instead joins the placenta, which transfers materials to and from the maternal blood without allowing direct mixing. The length of the umbilical cord is approximately equal to the crown-rump length of the fetus throughout pregnancy. The umbilical cord in a full term neonate is usually about 50 centimeters (20 in) long and about 2 centimeters (0.75 in) in
Social uterus Social uterus Social uterus is a developmental concept in family therapy for psychosomatic disorders. Social uterus as an integrative model of family development was invented by Vladislav Chvála and Ludmila Trapková in 1990's. The metaphor of a social uterus was formed by comparing the biological function of the uterus and the maturation of the foetus inside it from conception to childbirth with the changes in the family from the birth of the child up to its separation around the age of 18. The metaphor translates facts well known from the biology of reproduction to the social level. In the "social