fetal circulation for the basic point of view

1. GOOD MORNING

2. FETAL CIRCULATION By: Ms.Sangeetha.X lecturer M.S.R.I.N.E.R.

3. INTRAUTERINE DEVELOPMENT OF CARDIOVASCULOR SYSTEM Single heart tube formed by- 16 th day Heart beating – 24 th day Development of heart septum & champers during 6-7 th week. Heart beat heard by Doppler by 10 -12 th week of pregnancy

4. ECG may be recorded by 11 – 20 th week. Fetal blood exchanges nutrients with maternal circulation across the chorionic villi by 3 rd week

5. Specific structures in intrauterine fetal circulation Blood enters lung but not for gas exchange Specific structures: 1.The umbilical vein 2.Ductus venosus 3.The foramen ovale 4.Ductus arteriosus 5.The hypo gastric arteries

6. 1.The umbilical vein: Highly oxygenated blood from the placenta enters to fetus through umbilical vein. It has a branch that joins the portal vein and supplies the liver.

7. 2.Ductus venosus : Connects umbilical vein to inferior venacava Blood mixes with deoxygenated blood returning from lower parts of the body. 3.The foramen ovale : Temporary opening between atria Allows blood entering from the inferior venacava to across into left atrium. Blood does not need to pass through the lungs to collect oxygen.

8. 4.Ductus arteriosus : Leads from the bifurcation of the pulmonary artery to the descending aorta. Just beyond the point where the sub clavian and carotid arteries leave. 5.The hypo gastric arteries / umblical arteries: Branch off from internal iliac arteries Become umbilical artery when it enter the umbilical cord. Return blood to the placenta.

9. THE PROCESS OF FETAL CIRCULATION: The blood takes half a minute circulate The umbilical vein carrying the oxygenated blood [80% saturated ] from the placenta, enters the fetus

10. CHANGES AT BIRTH DUE TO Cessation of the placental blood flow Initiation of respiration 1.Closure of umbilical arteries: Functional closure – instantaneous [ preventing fetal blood to drain out ] Actual obliteration – 2-3 months First few centimeters - Obliterarted hypo gastric arteries and the proximal parts remain open as superior vesical arteries.

11. 2.Closure of umbilical veins & Ductus venosus : Obliteration little later than arteries [ allowing few extra volume of blood 80-100ml to be received by the fetus from placenta]. Ductus venosus collapses Venus pressure of inferior vena cava falls So right atrial pressure also fall. After obliteration the umbilical vein become ligamentum teres , Ductus venosus become ligamentum venosus .

12. 3.Closure of the Ductus arteriosus : Constriction of ductus arteriosus due to rising oxygen tension of the blood through the duct This effect mediated through the action of prostoglandins Functional closure soon after establishment of pulmonary circulation Anatomical-1-3 months & become ligamentum arteriosum

13. 4.Closure of foramen ovale : By increased pressure of the left atrium combined with decreased pressure of right atrium Functional closure – soon after birth Anatomical – about 1 year First few days closure may be reversible Cyanotic look during cry

14. Adaptations to extrauterine life 1.The umbilical vein 2.Ductus venosus 3.The foramen ovale 4.Ductus arteriosus 5.The hypo gastric arteries 1.Ligamantum teres 2. Ligamantum venosum 3.Fosa ovalis 4. Ligamantum arteriosum 5.Obliterarted hypo gastric arteries / superior vesical arteries

15. Estimated cardiac output 1-2 hour after birth is 500ml/min Heart rate 120-140/min.

16. Complication 1.Atrial septal defect [foramen ovale closure failure] 2.Patent ductus arteriosus [failure of ductus arteriosus closure]