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FETAL CIRCULATION S-2-CVSM72 LEARNING OBJECTIVES At the end the lecture the student should know the following: Problems with persistence of fetal circulation after birth FETAL CIRCULATION functioning. low to placenta. UMBILICAL VESSELS Located at the navel and enters the liver THE PLACENTA SHUNTS OF THE FETAL HEART Foramen ovale Connection between the right and left atria Ductusarteriosus Connection between the truncuspulmonalis and the aorta FORAMEN OVALE -flow. left atrium, skipping the lungs. -third of blood takes this route. DUCTUS ARTERIOSUS ary trunk. ductusarteriosus. UMBILICAL VEIN TO PORTAL CIRCULATION irculation allowing the liver to process nutrients. jority of the blood enters the ductusvenosus, a shunt which bypasses the liver and puts blood into the hepatic veins. FETAL CIRCULATION ients from the placenta to the fetus e liver, other half into the ductus venous and then into the inferior vena cava IN THE RIGHT ATRIUM m the superior vena cava. pulmonary veins. e heart and brain REMAINING BLOOD IN RIGHT ATRIUM pulmonary artery. ductusarteriosus. t 15% of the blood flows through lungs to the right atrium by way of the pulmonary veins INTERNAL ILIAC ARTERIES nch into the external and internal iliacs. back to the placenta to gather oxygen and to get rid of the waste products. FINALLY THE BIRTH!!! o thermal., tactile and visual o Results in a decrease in fetal blood PO2, increase in PCO2 and pH to decrease AT BIRTH from fetal to postnatal circulation happens very quickly. AFTER BIRTH? and liver functions are working the fetal circulation undergoes some changes since they are no longer needed FETAL LUNG FLUID functional residual capacity (FRC) 1/3rd of the fluid is squeezed out of the lungs as the baby passes through the birth canal FIRST BREATH be generated to overcome the viscous fluid found in the lungs. This pressure is -40cmH20. Up to 100cmH20! exhaled. The remaining amounts help to create the residual volume s .005L/cmH20 and the airway resistance is 30cmH20/L/sec CHANGES IN CIRCULATION ce falls. xic vasoconstriction caliber of the extra alveolar vessels AS THE PVR DECREASES….. blood flows through the lungs which allows for more blood to come to the left atrium. The results in a increase pressure in the left atrium which allows the flap of the foramen ovale to close. The closure is also helped by the fall in pressure in the right atrium as the umbilical flow stops. ue to the increase in PO2. EFFECTS OF INCREASED PO2 -50mmHg to allow the ductusarteriosus to close. If it is not reached the ductus will not close and the PVR will remain elevated causing Persistent Pulmonary Hypertension of the Newborn (PPHN) -48 hours after birth the ductus will re open VITAL SIGNS OF THE NEWBORN -50/min 130-150/min -70/45 PERSISTENCE OF FETAL CIRCULATION: nt foramen ovale each characterize about 8% of congenital heart defects. -rich and oxygen-poor blood; blood reaching tissues not fully oxygenated. Can cause cyanosis. around age two. TREATMENT methacin (prostaglandin synthetase inhibitor)
