Amniotic liquid
From ChildWiki.com
Amniotic liquid is a biological product that fills in the amniotic cavity, forming the fetal environment, allowing the fetus, after he gets detached and remains linked to the placenta only by the umbilical cord to move freely inside the uterus. It has a role in mechanically protecting the fetus and also in nutrition and fetal maturation.
It allows the fetus to mature, to be thermally isolated and stops germs and bacteria from going in.
During labor, it acts like a lubricant that makes sure the baby progresses inside the birth canal.
Amniotic liquid has a double origin: maternal and fetal. At the beginning of the pregnancy, when the embryo is very small, it is a product of active secretion (a secretion that requires energy). Later on, it will be produced by ultra-filtering through fetal skin, and after the 5th month it will be mostly produced by fetal urine and fetal lungs secretions. The fetus is indispensable for producing amniotic liquid, and the latter appears even if the egg is not fecundated properly. It is certain that there is an exchange through membranes without modifying the quantity of liquid.
The secretion of the amniotic liquid is assured both by the placenta and the membranes, by the mother, by passing protein free liquid from her blood to the amniotic cavity,but also by the fetus and the umbilical cord.
Until the 4th month of pregnancy, the liquid looks like an extension of the extracellular fetal space, because the liquid passes freely through fetal skin, which in completely permeable. Its composition will modify during the last half of the pregnancy, when the fetal skin will no longer be permeable and its organs will start functioning.
The fetal skin becomes impermeable by the end of the 4th month. Fetal urine starts to have a role in producing amniotic liquid at the end of the first trimester, and later on it will be the main producer.
Fetal deglutition also has an important role in maintaining the volume of the amniotic liquid. The fetus starts having respiratory movements, and the lungs are full of amniotic liquid that is changed once in a while.
