Study Question Sixteen

• Q16. Trace the pattern of fetal circulation and changes in fetal circulation that occur at birth; emphasize the following structures: foramen ovale (becomes fossa ovale/ovalis), ductus arteriosus (becomes ligamentum arteriosum, ductus venosus (becomes round ligament of liver). 
• Fetal Circulation - Start to Finish

  • Placenta
  • Umbilical Veins
  • Ductus Venosus
  • Foramen Ovale
  • Ductus Arteriosus
  • Umbilical Arteries
• • Placenta
  • Oxygenated blood from here enters the fetus.
• • Umbilical Veins
  • Contain oxygenated blood, starting from the placenta. Carries oxygenated blood toward the inferior vena cava through...
• • Ductus Venosus
  • Short vessel that connects the umbilical vein to the inferior vena cava, bypassing the liver. This allows most of the oxygenated blood to flow directly into the right atrium of the heart.
• • Foramen Ovale
  • Oxygenated blood enters the right atrium from the inferior vena cava, then moves into the left atrium through this structure. This structure is a hole in the interatrial septum. This allows the blood to bypass the lungs that aren't functional.
  • From the left atrium, blood flows into left ventricle then aorta, supplying brain and body.
• • Ductus Arteriosus
  • Blood entering right atrium and right ventricle, directed to pulmonary artery. This structure is a vessel connecting the pulmonary artery and aorta, allowing most of the blood to bypass the lungs and flow into the systemic circulation.
• • Umbilical Arteries
  • Carry deoxygenated blood from the fetus and returns it to the placenta. There are two of this structure. They branch rom the internal iliac arteries. Carry waste and carbon dioxide away from the fetus.
• After Birth

  • Ductus Venosus closes, becomes the ligamentum venosum and allows liver to function.
  • Foramen Ovale closes, becomes fossa ovalis, no longer allowing blood to bypass the lungs.
  • Ductus Arteriosus closes, blocking off the pathway between the aorta and pulmonary trunk, no longer bypassing the lungs. Becomes the ligamentum arteriosum.
• Trace fetal circulation.

  Oxygenated blood enters through the placenta, and flows through umbilical veins. The ductus venosus connects the inferior vena cava to the umbilical veins, bypasses the liver, allowing the blood to continue to the right atrium. Then blood can bypass pulmonary circuit, due to the foramen ovale, which is a hole in the interatrial septum, so blood goes to left atrium. Blood avoids the lungs by ductus arteriosus, a structure between the pulmonary trunk and the aorta. Umbilical arteries carry waste and deoxygenated blood back toward the placeta.
• Trace the pattern of fetal circulation and changes in fetal circulation that occur at birth. 

  After birth, many of the structures that allowed blood to bypass certain structures are no longer needed. The ductus venosus closes, now allowing blood through the liver, and the structure becomes the ligamentum venosus. Similarly, the foramen ovale closes, no longer allowing blood to skip the pulmonary circuit, and the structure becomes the fossa ovalis. The ductus arteriosus which also allowed blood to bypass the pulmonary circuit, closes as well and becomes the ligamentum arteriosum.