Fetal blood circulation

All that is necessary for development, the fetus receives from the blood of the mother. Maternal blood through the uterine artery penetrates into the placenta ("child's place"). The blood of the mother and fetus in the placenta is not mixed, therefore the blood circulation of the fetus is called placental. In the placenta, fetal blood receives nutrients from the maternal blood through the hematoplacental barrier. From the placenta arterial blood enters the umbilical vein of the fetus, which, in the umbilical cord, goes to the lower edge of the liver, lies in the furrow of the umbilical vein and divides into two branches at the level of the lobes of the liver. The first branch falls into the portal vein, and the second branch - the venous (ductus venousus) - into one of the hepatic veins or into the inferior vena cava. Thus, the arterial blood that flows through the umbilical vein from the placenta partially enters directly into the inferior vena cava, and partly into the liver, which is the fetus's organ of hematopoiesis. Further through the hepatic veins, blood enters the inferior vena cava, where it mixes with the venous blood flowing from the lower part of the trunk of the fetus. In the inferior vena cava, mixed blood enters the right atrium. From this pre-injury, through the oval aperture of the interatrial septum, the blood enters the left atrium, where its current is guided by a distinctly developed vestibule of the inferior vena cava (eustachian valve) in the fetus. From the left atrium, the blood enters the left ventricle, and then it goes to the organs and tissues of the fetal body along the aorta and the outgoing arteries.

Venous blood from the upper fetal body enters the right atrium along the superior vena cava. Through the right atrioventricular vent this venous blood passes into the right ventricle. From the ventricle, the blood flows into the pulmonary trunk, and then flows along the large arterial (ductal) ductus (ductus arteriosus) directly into the aorta (below the left subclavian artery). In the aorta to the mixed blood, which came from the left ventricle, new portions of venous blood from the right ventricle are added. This mixed blood flows down the branches of the descending aorta to all the organs and walls of the lower half of the fetal body. Thus, the upper half of the fetal body (in particular, the brain), which is supplied with blood from the branches of the aortic arch, leaving it before the admission of the arterial duct (common carotid and subclavian arteries), receives blood richer in oxygen and nutrients than the lower half .

Enrichment of fetal blood with oxygen and nutrients occurs in the placenta, where the mixed blood from the aorta follows through the internal iliac arteries, and then along its branches - the paired umbilical artery - into the placenta.

After birth in the vascular system of the newborn there are significant changes. Placental circulation is abruptly replaced by pulmonary circulation. Light, pulmonary arteries and veins begin to function. Bandaged after birth umbilical vessels empty: the trunk of the umbilical vein turns into a circular ligament of the liver, and the umbilical arteries into the right and left lateral umbilical ligaments; the lumen of the arteries is preserved only in their initial section. These umbilical ligaments are located on the back surface of the anterior abdominal wall. The venous duct becomes a venous ligament; the arterial duct, which in the fetus connected the pulmonary trunk with the concave part of the arch of the aorta, becomes an arterial ligament connecting the trunk (or the left pulmonary artery) with the arch of the aorta.

[1], [2], [3], [4], [5], [6]