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Unformatted text preview: d lower limbs. Ductus venosus has a physiological sphincter to control blood flow into the heart. Note the areas of Mixing of Oxygenated and less oxynated blood Changes in the circulation after birth. Changes After birth circulatory changes take place over a period of time: Occlusion of placental circulation by separation of the placenta by cutting off/ligation the umbilical cord As soon as the oxygenation from placenta is disturbed lungs take over: Functional expansion of the baby’s lungs with the 1st breath Pulmonary vascular resistance decreases at this point Rt.atrial pressure decreases, Lt. atrial pressure increases Closure of foramen ovali Fetal shunts that by pass liver and lungs start to close – ductus venosus is the main bypass, when input from d.v. is reduced, naturally right atrial pressure decreases and so left atrial pressure increases because most of the blood is coming from the lungs now and the pulmonary veins are bringing in more blood than before resulting in the foramen ovale closing off because if you have it still o...
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