The fetal circulatory system differs significantly from the postnatal circulatory system in several ways. During fetal development, gas exchange occurs via the placenta rather than the lungs. As a result, the fetal circulatory system has four unique shunts that allow blood to bypass the lungs, including the foramen ovale, ductus arteriosus, ductus venosus, and umbilical vessels. This allows oxygenated blood from the placenta to reach the upper body while less oxygenated blood is shunted to the lower body and placenta for reoxygenation. At birth, closure of the shunts and expansion of the lungs causes the circulatory system to transition to adult configuration with

1. Subject: ANATOMY
PRESENTED BY: komal zulfiqar

3. Introduction:
"Nature is neither lazy nor devoid of foresight.
Having given the matter thought, she knows in
advance that the lung of the fetus does not require
the same arrangements of a perfected lung. She
has therefore anastomosed the pulmonary artery
with the aorta, and the left and right atria. . . .“
-Galen, 2nd Century

4. FETAL NEWBORN
Gas exchange Placenta Lungs
RV,LV circuit Parallel Series
Pulmonary circulation Vasoconstricted Dilated
Fetal myocardium
Contractility,Compliance Less Good
Dominant ventricle Right Left
Change in Structure Umbilical vein
Umbilical artery
Ductus venosus
Ductus arteriosus
Foramen ovale
Ligamentum teres
Medial umb ligament
Ligamentum venosum
Ligamentum arteriosum
Fossa ovalis

5. 4 UNIQUE FETAL CVS STRUCTURES :FOUR
SHUNTS

6. COURSE OF FETAL
CIRCULATION:
1.Placenta:
Has the lowest vascular resistance in the fetus.
Receives the largest amount of combined (Rt +
Lt) Ventricular Output (55%)

7. 2. Superior Vena Cava:
Drains the upper part of the body,including the brain (15% of
combined ventricular output).
Most of SVC blood goes to the Right Ventricle.

8. 3. INFERIOR VENA
CAVA:
DRAINS LOWER PART OF
BODY AND PLACENTA (70%
OF COMBINED VENTRICULAR
OUTPUT)
Part of IVC blood with high O2
goes into LA via Foramen Ovale.
Remaining IVC blood enter RV
and Pulmonary artery.
Since blood is
oxygenated in the
placenta, Oxygen
saturation in IVC
(PO2 =26-28%) is higher
than that in SVC (12-14%).

9. COURSE OF FETAL CIRCULATION:
Most of SVC blood (less oxygenated blood) goes intoRV.
Most of IVC blood (high O2 concentration) is directed by theCrista
Dividens to the LA through Foramen ovale.
Rest of IVC blood enters RV & pulmonaryartery.
Less oxygenated blood in Pulmonary artery flows through Ductus
Arteriosus to descending aorta and then to placenta for
oxygenation.

10. COURSE OF FETAL CIRCULATION:
The Result is:
Brain and coronary circulation receive blood with higher
concentration (PO2 = 28 mm Hg) than the lower part of the
body (PO2 = 24 mm Hg)

11. FETAL CIRCULATION: THE PATHWAY:
PLACENTA  OXYGENATED BLOOD UMBILICAL VEIN
Hepatic
circulation
Bypasses liver & joins
IVC via ductus
venosus
Partially mixes with poorly oxygenated
IVC blood derived from lower part of
fetal body

12. FETAL CIRCULATION:
Combined lower body blood plus umbilical venous
blood flow (PO2 of ≈26–28 mm Hg) passes through
IVC to the Right atrium and is preferentially
directed across the foramen ovale to the left atrium.
The blood then flows into the left ventricle and is
ejected into the ascending aorta.
Fetal SVC blood, which is considerably less
oxygenated (PO2 of 12–14 mm Hg), enters the Right
atrium and preferentially traverses the tricuspid
valve, rather thanthe foramen ovale, and flows
primarily to the right ventricle.

13. FETAL CIRCULATION:
From the right ventricle  Pulmonary
artery.
Because the pulmonary arterial circulation is
vasoconstricted, only about 10% of right ventricular
outflow enters the lungs.
The rest 90% blood (which has a PO2 of ≈18–22 mm
Hg) bypasses the lungs and flows through the
ductus arteriosus into the descending aorta to
perfuse the lower part of the fetal body.
It the returns to the placenta via the two umbilical
arteries.

14. Thus, upper part of fetal body (including coronary & cerebral
arteries and those to upper extremities) is perfused exclusively
from the Left ventricle with blood that has a slightly higher PO2 ,
than the blood perfusing the lower part of the fetal body, which
is derived mostly from the Right ventricle.
Only a small volume of blood from the ascending aorta (10% of
fetal cardiac output) flows across the aortic isthmus to the
descending aorta.

15. Thus, upper part of fetal body (including coronary & cerebral
arteries and those to upper extremities) is perfused exclusively
from the Left ventricle with blood that has a slightly higher PO2 ,
than the blood perfusing the lower part of the fetal body, which
is derived mostly from the Right ventricle.
Only a small volume of blood from the ascending aorta (10% of
fetal cardiac output) flows across the aortic isthmus to the
descending aorta.

16. LA  LV  AORTA  DUCTUS ARTERIOSUS
Foramen ovale RV
SVC  upper body
IVC
50% through
ductus venosus
50% to
Portal circulation
Umbilical Vein
Oxy.blood
PLACENTA

17. AORTA
Deoxygenated blood
Descending aorta
Abdominal aorta
Common iliac artery
Umbilical arteries
PLACENTA
Oxygenation
Umbilical Vein

18. FETAL CIRCULATION:
The total fetal cardiac output—the combined output of both
the left and right ventricles—is ≈450mL/kg/min.
Descending aortic blood flow :
-65%  returns to placenta;
-Remaining 35%  perfuses the fetal organs & tissues.
Right ventricular output is about 1.3 times the left
ventricular flow.
Thus, during fetal life the rightventricle
-is pumping against systemic blood pressure
-is performing greater volume of work than LV.

19. Changes in fetal
circulation AFTER BIRTH

20. Changes in fetal circulation after birth

21. FETAL VS INFANT CIRCULATION
FETAL INFANT
 • Low pressure system
 • Right to left shunting
 • Lungs non-functional
 • Increased pulmonary
resistance
 • Decreased systemic
resistance
 •High pressure system
 •Left to right blood flow
 •Lungs functional
 •Decreased pulmonary
resistance
 •Increased systemic resistance
INFANT
FETAL

24. THANK YOU