FETAL AND NEONATAL CIRCULATION lecture.pptx

Fetal circulation

1. FETAL AND NEONATAL CIRCULATION DR KELECHI DURUH DEPARTMENT OF HUMAN ANATOMY FBMS COLLEGE OF MEDICINE UNEC 27/7/23 BY

2. OUTLINE INTRODUCTION FETAL CIRCULATION TRANSITIONAL CHANGES/TRANSITIONAL NEONATAL CIRCULATION DERIVATIVES FROM THE TRANSITIONAL CHANGES CLINICAL CORRELATES 1

3. INTRODUCTION In fetal circulation, the placenta supplies oxygen, nutrition and aids in detoxification. The lungs are non-functional Shunts exist bypassing the lungs and liver Though the partial Oxygen pressure is relatively low, tissues are adequately supplied Fetal circulatory system provides prenatal and perinatal needs and allows for modification at birth 2

4. INTRODUCTION contd . Modifications establish neonetal circulatory pattern In neonatal circulation, the lungs are aerated The severance of placenta from the fetus has consequential changes Some circulatory components undergo functional and anatomical changes Changes bring about directional and dynamic alterations in blood flow 3

5. FETAL AND NEONATAL CIRCULATIONS FETAL CIRCULATION NEONATAL CIRCULATION 4

6. FETAL CIRCULATION Oxygenated, nutrient rich blood from placenta passes through the umbilical vein At the area of the liver, 50% pass through the ductus venosus (DV) into the IVC The other 50% pass through the portal sinus , the portal vein, liver sinusoids, hepatic veins into the IVC A sphincter in the DV regulates blood flow Contraction of sphincter reduces flow through the DV increasing flow through liver sinusoids 5

7. FETAL CIRCULATION contd The IVC drains the DV, hepatic veins and the abdominal vein After a short course the IVC, empties into the right atrium Most blood arriving right atrium from IVC are directed through the foramen ovale into the left atrium In the left atrium ,it mixes with a small quantity of poorly oxygenated blood returning from the pulmonary veins Left atrium empties into the left ventricle 6

8. FETAL CIRCULATION contd. FORAMEN OVALE 7

9. FETAL CIRCULATION contd Left ventricle transmits blood through the ascending aorta , the arch, the descending aorta, to the arteries of the trunk and lower body The ascending aorta supplies the heart The arch supplies the head ,neck and upper limbs The residual volume of blood in the right atrium mixes with poorly oxygenated blood from SVC and coronary sinus and enters the right ventricle The right ventricle ejects blood through the pulmonary trunk 8

10. FETAL CIRCULATION contd Pulmonary vascular resistance is higher than that of the systemic 90% of pulmonary trunk blood pass through the ductus arteriosus (DA) into the descending aorta 10% goes to nourish the lungs DA protects the lungs from circulatory overload also aids the right ventricle in adjusting to postnatal functioning 9

11. FETAL CIRCULATION contd 65% of blood in the descending aorta passes into the umbilical arteries into the placenta 35% nourishes the viscera and inferior part of the body then returns to the heart through IVC and SVC 90% of left ventricular ejection nourishes the head, neck and upper limb 10% pass down to the descending aorta 10

12. TRANSITIONAL NEONATAL CIRCULATION Change from fetal to neonatal circulation is not sudden occurrence Some occur with first breath others over hours or days The closure of fetal vessels and oval foramen is initially a functional change then anatomical At cessation of placental flow, changes occur to exclude placenta in the circulation Shunt points are shut down 11

13. TRANSITIONAL NEONATAL CIRCULATION The foramen ovale , DA, DV and umbilical vessels become needless DV sphincter constricts , diverting all blood to portal vein Pressure in IVC and right atrium consequently reduce Lung expansion and aeration causes decrease in pulmonary vascular resistance and increase in pulmonary flow Stretching of the lungs causes thinning of pulmonary artery walls 12

14. TRANSITIONAL NEONATAL CIRCULATION 13

15. TRANSITIONAL NEONATAL CIRCULATION 14

16. TRANSITIONAL NEONATAL CIRCULATION contd. Increased pulmonary flow and cessation of umbilical flow reduces pressure in the right heart Increased pulmonary venous return builds left atrial pressure Higher pressure in the left atrium relative to right functionally closes the foramen ovale DA constricts at birth 15

17. TRANSITIONAL NEONATAL CIRCULATION contd. Small volume flow from descending aorta into pulmonary trunk may linger for about 72hrs By 96hrs 100% of DA should be functionally closed Oxygen is the main enhancing factor Closure is mediated by prostaglandin E2 and bradykinin Factors that may impede normal closure include prematurity, hypoxia etc 16

18. TRANSITIONAL NEONATAL CIRCULATION contd. DA constricts when PaO2 of blood in the aorta approximates 50mmHg During fetal life ,patency of DA is maintained by low oxygen and some endogenous prostaglandins Umbilical arteries constricts at birth Blood flow in the vein continues for 1min or more prior to tying of cord 17

19. DERIVATIVES OF FETAL VASCULAR STRUCTURES Certain fetal vessels and structures are undesired in extrauterine circulation Within a period of time these fetal vessels form nonfunctional ligaments The umbilical vein remains patent for considerable time The intraabdominal part eventually becomes the round ligament 18

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21. DERIVATIVES OF FETAL VASCULAR STRUCTURES contd. UMBILICAL VEIN, DUCTUS VENOSUS 20

22. DERIVATIVES OF FETAL VASCULAR STRUCTURES contd. DV becomes ligamentum venosum Distal part of umbilical arteries become the medial umbilical ligament The proximal part persist as the superior vesical arteries Foramen ovale closes functionally at birth then anatomically by 3 rd month 21

23. DERIVATIVES OF FETAL VASCULAR STRUCTURES contd. The septum primum forms the floor of the oval fossa The inferior edge of the septum secundum forms the rounded fold DA closes functionally within first four days of birth Anatomical closure and formation of ligamentum arteriosum occurs at 12 th postnatal week 22

24. CLINICAL CORRELATES Patent ductus arteriosus Coartation of the aorta Double IVC, non formation of IVC Patent foramen ovale Pulmonary stenosis Double arch of the aorta Abnormal origin rt.subclavian 23

25. CLINICAL CORRELATES PATENT DUCTUS ARTERIOSUS 24

26. CLINICAL CORRELATES PRE AND POST-DUCTAL COARTATIONS OF THE AORTA 25

27. CLINICAL CORRELATES PATENT FORAMEN OVALE 26

28. GOD BLESS YOU 27