If it is important to know the meaning of the term chorion, it is also important to discover its etymological origin. In this case, we can state that it is a neologism that took shape in the Renaissance. Neologism that was based on the Latin word “corium”, which comes from the Greek “khorion”, which means “membrane”.
The idea came to our language as a chorion : this is the name given to the outer envelope of the embryo of mammals, birds and reptiles.
In the case of most mammals, the chorion surrounds the amnion and contributes to the development of the placenta (the organ from which the umbilical cord arises and allows it to mediate between the mother and the developing embryo). Villi emerge from the chorion and penetrate the endometrium and enable an exchange of nutritional substances to occur.
In an amniote egg there are three extraembryonic membranes : the chorion, the allantois and the amnion. In this aqueous medium the embryo receives food and breathes. The egg also has a calcareous envelope that provides protection.
The development of embryos, in short, is very different depending on the species. The young of birds and other species develop inside an egg, in which the yolk sac contains blood vessels that enable the transport of nutrients. In humans , however, nutrients arrive through the endometrium.
As gestation progresses, the chorion ends up becoming the placenta , while its inner layer fuses with the amnion. In the chorion, on the other hand, the production of the hormone human chorionic gonadotropin takes place. It can be said that the placenta is a structure that, arising from the chorion of the fetus and the uterine endometrium, is composed of fetal and maternal elements.
In addition to everything stated above, we cannot ignore another series of relevant aspects about the chorion, among which the following must be highlighted:
-It plays an essential role in the respiratory process of the baby that is on the way.
-It has the appearance of concentric circles, which have several layers. Exactly we can determine that there are two: the internal one, which is the one that is directly in contact with what the embryo is, and the external one. This, for its part, is the one that is characterized because it is in direct contact with what the mother is.
-In the same way, the aforementioned internal layer is made up of the so-called mesoderm, which plays an essential role in the formation of the fetus.
-The outer layer, on the other hand, is composed of what is called troboblast, which becomes vital in the nutrition of the embryo.
-In most cases, when various complications arise during the first trimester of pregnancy, it is because there are problems in the chorion, that is, it has not formed properly.