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Transcript of Fetal circulation
In an adult, arteries carry blood away from the heart and veins carry the blood back to the heart where in a fetus the arteries carry non-oxygenated blood back to the heart and veins carry oxygenated blood away from the heart Another difference is that a fetus does not get oxygen from inhaling it like we do and gas exchange does not happens in the lungs, instead it gets oxygen from the umbilical cored that is attached to the mother and the gas exchange happens in the placenta. In an adult or child there is more pressure on the left side of heart but in a fetus the increased pressure is on the right side of the heart.
there are two main structural differences. A fetus has a Foramen Ovale and ductus arteriosus to help reroute the blood. For most of it's time in the womb the fetuses lungs are collapsed and not functional.
Blood flow to the placenta is provided by a pair of umbilical arteries which arise from the internal iliac arteries and enter the umbilical cord. Blood returns from the placenta in the single umbilical vein, bringing oxygen and nutrients to the developing fetus. Fetal circulation sequence Exchange of gases occurs in the placenta. Oxygenated blood is carried by the umbilical vein towards the fetal heart. The ductus venosus directs part of the blood flow from the umbilical vein away from the fetal liver (filtration of the blood by the liver is unnecessary during the fetal life) and directly to the inferior vena cava. Blood from the ductus venosus enters to the inferior vena cava. Increase levels of oxygenated blood flows into the right atrium. In adults, the increase pressure of the right atrium causes the tricuspid valve to open thus, draining the blood into the right ventricle. However, in fetal circulation most of the blood in the right atrium is directed by the foramen ovale (opening between the two atria) to the left atrium. The blood then flows to the left atrium to the left ventricle going to the aorta. Majority of the blood in the ascending aorta goes to the brain, heart, head and upper body. The portion of the blood that drained into the right ventricle passes to the pulmonary artery. As blood enters the pulmonary artery (carries blood to the lungs), an opening called ductus arteriosus connects the pulmonary artery and the descending aorta. Hence, most of the blood will bypass the non-functioning fetal lungs and will be distributed to the different parts of the body. A small portion of the oxygenated blood that enters the lungs remains there for fetal lung maturity. The umbilical arteries then carry the non-oxygenated blood away from the heart to the placenta for oxygenation. What is a blue baby A 'blue baby' happens when a baby is born but the foramen ovale or the ductus arteriosus has not closed and the baby is not getting any oxygen because the blood is still bypassing the lungs.
Prompt treatment is required and the foramen ovale or ductus arteriosus is surgically closed and blood flow is corrected. A fetal hear beats anywhere from 120 beats to 160 beats per minute When the baby is born it takes a breath and starts regular circulation.