Foetal CirculationFoetal Circulation

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Fetal CirculationFetal Circulation

By the third month of development, all By the third month of development, all major blood vessels are present and major blood vessels are present and functioning.functioning.

Fetus must have blood flow to placenta.Fetus must have blood flow to placenta.

Resistance to blood flow is high in Resistance to blood flow is high in lungs.lungs.

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Umbilical CirculationUmbilical Circulation Pair of umbilical Pair of umbilical

arteries carry arteries carry deoxygenated deoxygenated blood & wastes blood & wastes to placenta.to placenta.

Umbilical vein Umbilical vein carries carries oxygenated oxygenated blood and blood and nutrients from nutrients from the placenta.the placenta.

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The PlacentaThe Placenta

Facilitates gas and Facilitates gas and nutrient exchange nutrient exchange between maternal between maternal and foetal blood.and foetal blood.

The blood itself The blood itself does not mix.does not mix.

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Umbilical vein to portal Umbilical vein to portal circulationcirculation

Some blood from the Some blood from the umbilical vein enters umbilical vein enters the portal circulation the portal circulation allowing the liver to allowing the liver to process nutrients.process nutrients.

The majority of the The majority of the blood enters the ductus blood enters the ductus venosus, a shunt which venosus, a shunt which bypasses the liver and bypasses the liver and puts blood into the puts blood into the hepatic veins.hepatic veins.

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foramen ovaleforamen ovale Blood is shunted Blood is shunted

from right atrium to from right atrium to left atrium, skipping left atrium, skipping the lungs.the lungs.

More than one-third More than one-third of blood takes this of blood takes this route.route.

Is a valve with two Is a valve with two flaps that prevent flaps that prevent back-flow.back-flow.

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ductus arterioususductus arteriousus

The blood pumped The blood pumped from the right from the right ventricle enters the ventricle enters the pulmonary trunk. pulmonary trunk.

Most of this blood Most of this blood is shunted into the is shunted into the aortic arch through aortic arch through the ductus the ductus arteriousus.arteriousus.

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What happens at birth?What happens at birth? The change from foetal to postnatal The change from foetal to postnatal

circulation happens very quickly.circulation happens very quickly. Changes are initiated by baby’s first Changes are initiated by baby’s first

breath.breath.

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Foramen ovaleForamen ovale Closes shortly after Closes shortly after birth, fuses completely birth, fuses completely in first year.in first year.

Ductus arterioususDuctus arteriousus Closes soon after birth, Closes soon after birth, becomes ligamentum becomes ligamentum arteriousum in about 3 arteriousum in about 3 months.months.

Ductus venosusDuctus venosus Ligamentum venosumLigamentum venosum

Umbilical arteriesUmbilical arteries Medial umbilical Medial umbilical ligamentsligaments

Umbilical vein Umbilical vein Ligamentum teresLigamentum teres

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Problem with persistence Problem with persistence of foetal circulationof foetal circulation

Patent (open) ductus arteriosus and patent Patent (open) ductus arteriosus and patent foramen ovale each characterizes about foramen ovale each characterizes about 8% of congenital heart defects. 8% of congenital heart defects.

Both cause a mixing of oxygen-rich and Both cause a mixing of oxygen-rich and oxygen-poor blood; blood reaching tissues oxygen-poor blood; blood reaching tissues not fully oxygenated. Can cause cyanosis.not fully oxygenated. Can cause cyanosis.

Surgical correction now available, ideally Surgical correction now available, ideally completed around age two.completed around age two.

Many of these defects go undetected until Many of these defects go undetected until child is at least school age.child is at least school age.

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