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Fetal Circulation Prepared by: Mrs. Mahdia Samaha Alkony.

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Presentation on theme: "Fetal Circulation Prepared by: Mrs. Mahdia Samaha Alkony."— Presentation transcript:

1 Fetal Circulation Prepared by: Mrs. Mahdia Samaha Alkony

2 Anatomy and Physiology Fetal Circulation Umbilical cord –2 umbilical arteries: return non-oxygenated blood, fecal waste, CO2 to placenta –1umbilical vein: brings oxygenated blood and nutrients to the fetus 5/3/20152Mahdia Shaker

3 Anatomy and Physiology Fetus depends on placenta to meet O2 needs while organs continue formation Oxygenated blood flows from the placenta To the fetus via the umbilical vein After reaching fetus the blood flows through the inferior vena cava 5/3/20153Mahdia Shaker

4 4 The differences between fetal and newborn circulation The fetus received oxygen from the placenta and through the lungs after birth. The fetal liver doesn’t have the metabolic function that it will have after birth because the mother performs these functions. Three shunts are present in fetal life: 1.Ductus venosus: connects the umbilical vein to the inferior vena cava 2.Ductus arteriosus: connects the main pulmonary artery to the aorta 3.Foramen ovale: anatomic opening between the right and left atrium. 5/3/2015

5 Fetal Circulation Blood travels from the inferior vena cava to the ductus venosis Ductus Venosis –Small amount of blood routed to growing liver –Increased blood flow leads to large liver in newborns 5/3/20155Mahdia Shaker

6 Fetal Circulation Blood continues to travel up the inferior vena cava Empties into the right atrium of the heart The blood then passes to the left atrium through the foramen ovale Only about one-third of this blood reaches the lungs (due to high flow resistance since the lungs are not yet expanded, and due to hypoxic vasoconstriction 5/3/20156Mahdia Shaker

7 A/P Fetal Circulation Blood continues journey to the left ventricle blood is then pumped into the aorta Blood is circulated to the upper extremities Blood then returns to the right atrium 5/3/20157Mahdia Shaker

8 A/P Fetal Circulation From the right atrium, the blood goes to the right ventricle then to the pulmonary arteries Pulmonary arteries –Small amount goes to the maturing lungs Rest of blood is shunted away from lungs by ductous ateriosus back to aorta 5/3/20158Mahdia Shaker

9 A/P Fetal Circulation The placenta will re-supply the blood with oxygen Fetal circulation is a low-pressure system 5/3/20159Mahdia Shaker

10 As a result, the blood supplied to the lower half of the body has a relatively low O2 concentration(O2 saturation = 0.3). The majority of this blood returns via the umbilical arteries to the placenta, where it is oxygenated again 5/3/2015Mahdia Shaker10

11 A/P Fetal Circulation Low pressure system –Lungs are closed –Most oxygenated blood flows between the atria of the heart through the foramen ovale –This oxygen rich blood flows to the brain through the ductus arteriosus 5/3/201511Mahdia Shaker

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13 Conversion of Fetal to Infant Circulation At birth –Clamping the cord shuts down low-pressure system –Increased atmospheric pressure(increased systemic vascular resistance) causes lungs to inflate with oxygen –Lungs now become a low-pressure system 5/3/2015Mahdia Shaker13

14 Conversion: Fetal to Infant Circulation –Pressure from increased blood flow in the left side of the heart causes the foramen ovale to close –More heavily oxygenated blood passing by the ductus arteriosus causes it constrict –Functional closure of the foramen ovale and ductus arteriosus occurs soon after birth –Overall anatomic changes are not complete for weeks 5/3/2015Mahdia Shaker14

15 What happens to these special structures after birth? –Umbilical arteries atrophy –Umbilical vein becomes part of the fibrous support ligament for the liver –The foramen ovale, ductus arteriosus, ductus venosus atrophy and become fibrous ligaments 5/3/2015Mahdia Shaker15

16 Human Fetal Circulation 5/3/201516Mahdia Shaker

17 Overview of Conversion Umbilical cord is clamped Loose placenta Closure of ductus venosus Blood is transported to liver and portal system Increased systemic resistance Pressure in right atrium decreased Change from right to left shunting to left to right blood flow Increased O2 levels in pulmonary circulation Closure of the ductus arteriosus 5/3/2015Mahdia Shaker17

18 Loss of placenta also leads to: 1.First breath 2.Lungs expand and fluid is expelled 3.Decreased pulmonary resistance 4.Increased pressure in left atrium 5.Closure of foramen ovale Increased systemic resistance Pressure in right atrium decreased Change from right to left shunting to left to right blood flow Increased O2 levels in pulmonary circulation Closure of the ductus arteriosus 5/3/2015Mahdia Shaker18

19 Fetal vs. Infant Circulation Fetal Low pressure system Right to left shunting Lungs non-functional Increased pulmonary resistance Decreased systemic resistance Infant High pressure system Left to right blood flow Lungs functional Decreased pulmonary resistance Increased systemic resistance

20 Mahdia Shaker20 Shunts Occur when the foramen ovale or ductus arteriosus remains open, placing a strain on the heart. In patent foramen ovale (atrial septum defect), the blood flows from left atrium to right atrium (left-to-right shunt) lead to right ventricle (volume overload), lungs and then left atrium. In patent ductus arteriosus, the blood flows from aorta to pulmonary artery (= left-to-right shunt) leads to lungs (pressure overload) and then aorta.

21 Flow Chart of Fetal Circulation 5/3/201521Mahdia Shaker

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