The fetal circulation allows oxygenated blood from the placenta to bypass the lungs and circulate throughout the fetus's body. Key structures include the umbilical vein, which carries oxygenated blood from the placenta to the liver, the foramen ovale and ductus arteriosus which allow blood to bypass the lungs, and the umbilical arteries which return deoxygenated blood to the placenta. The circulatory process involves blood passing from the placenta through the umbilical vein, mixing with deoxygenated blood and passing through the foramen ovale and ductus arteriosus to supply the fetus before returning to the placenta through the umbilical arteries.

1. FETAL CIRCULATION
Presented by:
A.Priyadharshini M.Sc(N),
Lecturer,
Jai institute of nursing and
research,
Gwalior.

2. INTRODUCTION:
• The key to understand the fetal
circulation is the fact that oxygen is
derived from the placenta!
• In addition the placenta is the source
of nutrition and the site of
elimination of waste.

3. Temporary structures in
fetal period:
Umbilical vein
Umbilical arteries
Ductus venosus
Foramen ovale
Ductus arteriosus

4. Umbilical vein:
This vein leads from the umbilical
cord to the underside of the liver
and carries blood rich in oxygen and
nutrients. It has a branch and joins
the portal vein and supplies the liver.

5. The ductus venosus:
(from a vein to vein)
This connects the umbilical vein to
the inferior venacava. At this point
the blood mixes with the
deoxygenated blood returning from
the lower parts of the body. Thus
the blood throughout the body is at
best partially oxygenated.

6. The foramen ovale:
( oval opening)
This is a temporary opening
between the atria that allows the
majority of blood entering from the
inferior venacava to pass across into
the left atrium. The reason for this
diversion is that the blood does not
need to pass through the lungs to
collect oxygen.

7. The ductus arteriosus
( from artery to artery)
This leads from the bifurcation of
the pulmonary artery to the
descending aorta, entering it just
beyond the joint point where the
subclavian and carotid arteries leave.

8. Umbilical arteries:
These branch off from the internal
iliac arteries and become the
umbilical arteries when they enter
the umbilical cord. They return blood
to the placenta.

9. The circulatory process:
• The blood takes about half a minute
to circulate.
• From the placenta, blood passes along
the umbilical vein through the
abdominal wall to the under surface
of the liver. This is the only vessel in
the fetus that carries unmixed blood.

10. • The ductus venosus carries blood to
the inferior venacava where it mixes
with the blood from the lower body.
• From here the blood passes into the
right atrium and most of it is
directed across through the foramen
ovale into the left atrium.
• Following its normal route it enters
into the left ventricle and passes into
the aorta.

11. • The heart and brain receives a supply
of relatively high oxygenated blood
since the coronary and carotid
arteries are earlier branches of
aorta.
• The arms also benefit via the
subclavian arteries. Arms are well
developed for this reason.

12. • Blood collected from the upper parts
of the body returns to the right
atrium in the superior venacavaa.
This blood is depleted of oxygen and
nutrients.
• This stream of blood crosses the
stream entering from the inferior
venacava and passes into the right
ventricle.

13. • The two streams remain separate
because of the shape of the atrium
but there is a mixing of 25% of the
blood, allowing a little oxygen and
nutrients to be taken into the lungs
through the pulmonary artery. This is
necessary for the lung development.

14. • The remainder blood passes through
the ductus arteriosus to the aorta.
Blood continues along the aorta and
although low in oxygen, has sufficient
to supply the remaining organs and
legs.
• The internal iliac arteries lead into
the hypogastric arteries, which
return blood to the placenta via the
umbilical arteries.

15. • The remaining blood supplies the
lower limbs and returns to the
inferior venacava.

16. Flow Chart of Fetal Circulation