Fetal circulation

• The fetus does not use its lungs for gas exchange. Thus, the fetal circulatory system has a few unique features.
• Foramen ovale


  Passageway (hole) between the right atrium and the left atrium that exists in the heart of a fetus
• Ductus arteriosus


  Vessel which provides a short cut to the aorta. Any blood that does not enter the right ventricle and is pumped into pulmonary trunk is shunted through the ductus arteriosus to the aorta
• Umbilical arteries

  Take fetal blood to the placenta from the iliac arteries
• Ductus venosus


  Short vessel that exists as a short cut through the liver and connects the umbilical vein to the fetal inferior vena cava (since the blood does not have to be detoxified here since it was done in the mother)
• Fetal features!

  Foramen ovale, ductus arteriosis, ductus venosus, umbilical veins and arteries. (iliac arteries, placenta, umbilical cord)
• Blue Baby


  the foramen ovale after birth is the most common defect (the hole between the two atria does not close. (Normally, the lungs would expand and cause the heart to fill in quantity and a flap would normally close the opening but this does not happen with the blue baby condition) The passage of impure blood from the right to the left atrium. (some deoxygenated blood would then travel through the body instead of fully oxygenated blood) b) How is blue baby condition corrected? They insert/thread a catheter into the heart and seal the defect
• Ductus arteriosus - after birth

  The ductus arteriosus closes because endothelial cells divide and block off the duct. Remains are transformed into connective tissue.
• The Placenta

  The placenta is firmly attached to the uterine wall by the allantois and by fingerlike projections called the chorionic villi. The umbilical cord stretches between the placenta and the fetus. The placenta functions only before birth. At the placenta, an exchange of molecules between fetal and maternal blood takes place across the walls of the chorionic villi. Oxygen and nutrient molecules diffuse into the fetal blood, and carbon dioxide and urea diffuse out of the fetal blood.