Fetal circulation and changes after birth

  • Oxygenated blood
  • Placenta
  • Umbilical vein
  • Through liver
  • Ductus venosus
  • IVC  ⇐ Deoxygenated blood from lower limb
  • Right atrium
  • Foramen ovale (opening of IVC faces foramen ovale)
  • Left atrium
  • Left ventricle
  • Aorta which distributes blood

 

  • Deoxygenated blood
  • SVC
  • Right atrium
  • Right ventricle (septum secondum prevents from entering foramen ovale)
  • Pulmonary trunk
  • Ductus arteriosus
  • Arch of aorta
  • Mix with oxygenated blood
  • Common iliac artery  ⇒ External iliac artery (oxygenated blood to lower limbs)
  • Internal iliac artery
  • 2 Umbilical arteries
  • Placenta

 

Mixing of oxygenated and deoxygenated blood in fetus:

  • Liver – Umbilical vein (oxy) + Portal vein (deoxy)
  • IVC – Ductus venosus(oxy) + Blood from lower limb (deoxy)
  • Left atrium – Right atrium (oxy) + lung buds (deoxy)
  • Dorsal aorta – via ductus arteriosus

 

Changes in circulation after birth

Immediate:

  1. Pulmonary circulation starts – lungs expand, negative pressure, air suctioned
  2. Closure of foramen ovale – Pressure increases in left atrium due to pulmonary circulation, therefore septum primum and septum secondum pushed together
  3. Closure of ductus arteriosus to form ligamentum arteriosum. From pulmonary trunk to arch of aorta

Late:

  1. Ductus venosus forms ligamentum venosum of liver. From left portal vein to IVC
  2. Umbilical vein – ligamentum teres of liver. From umbilicus to left portal vein
  3. Umbilical artery – Lateral umbilical ligament. From superior vesical artery to urinary bladder.

 

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