1.Describe the feto – placental and maternoplacental
circulation.The placenta has its main function is to receive blood and
supplies the same to both maternal and the fetal systems. The maternal – placental
circulation initiates with the mother’s blood flowing through the spaces
between the intervillous capillaries. These capillaries are present on the
uterine decidual arteries. The diffusion process between oxygen and any other nutrients
occurs when the maternal blood persists around the terminal villi. Various theories for the maternoplacental circulation has been
described. The most common one describes the significance of trophoblasts in
the circulation. The trophoblasts invaginate into the decidual spiral arteries.
These are present perpendicular to the uterine wall whereas the veins are parallel.
This form of arrangement helps the veins to close during any contractions and permitting
the blood to flow from the maternal blood .Thus it forms trophoblastic plugs.
These then block the maternal blood flow into the intervillous spaces. The
obstructs the blood flow until the end of the first trimester After which the
plugs get weaken hence permits the flow . The maternal blood volume drastically
in the first week of pregnancy and then reached a maximum such that it remains
constant.The fetal-placental circulation permits the arteries of the
umbilical to carry deoxygenated blood. This transportation occurs from the
fetus to the villous vessels of the fetus. The vein of umbilical arrives oxygen
and nutrient-rich blood lack to the fetal circulation. This again tends to take
place after the exchange between oxygen and nutrients
Umbilical arteries 1 Spiral arteries
Umbilical vein 2
Fetal capillaries 3 Intervillous
A Basal layer
2.Trace the flow of blood in the fetal circulation, and state
the function of foramen ovale and ductus arteriosus.The fetal blood flow
circulation has more steps than after the baby is born, who has a normal heart.
The reason is the placenta does the work initially, which later the baby’s
lungs does. The deoxygenated blood which is darkish blue in color of the fetus
is received by the placenta and then exists out from the circulation through
the umbilical cord. The oxygenated blood then comes back to the fetus by the
vessels of umbilical cord, liver and right side of heart.
Inside the fetal heart:·
The blood that enters the right atrium move to the left atrium
of the heart by the the foramen ovale ·
Blood then passes into the left ventricle, then into the aorta. ·
From aorta, blood is sent to the heart muscle, brain and arms.
After circulation the same blood moves to the right atrium, but then next to
the superior vena cava. ·
The oxygenated blood is pumped from the right ventricle into the
aorta by the ductus arteriosus to the descending aorta. ·
This blood then passes into the umbilical arteries where they
finally reach the placenta. Functions of the shunts:The Ductus VenosusOxygenated
blood moves from the placenta across the umbilical vein and avoids the liver by the ductus venosus. It connects the umbilical vein to
the caudal vena cava.The Foramen OvaleThe foramen
ovale is an opening between the right and left atria. The septum secundum allows
the blood to enter right atrium through the foramen ovale into the left atrium.The Ductus ArteriosusThe ductus
arteriosus connects the pulmonary artery to the aorta. This permits equivalent
ventricular function in the fetus. The ductus arteriosus empties blood into the
aorta assuring that the brain receives appropriate oxygenated blood. 3. Explain
where the foramen ovale and ductus arteriosus are located, and describe their
purposeIn the fetal
heart, the foramen ovale is present at the junction of the right and left atrium.
In most individuals after birth the foramen ovale closes and then forms the
fossa ovalis. It develops in the fourth week of gestation. After birth,the
patent foramen ovale helps in blood flow from the venous to arterial parts.
This could lead to higher chances of stroke and ischemic attack.
developing fetus, ductus arteriosus is also called the ductus Botalli.
It mainly helps in connecting the pulmonary artery to descending aorta. It
functions as a bypass shunt to the liver. After birth, its closure forms the
liganmentum arteriosum. In the embryonic stage of development, it is formed by
the 6th aortic branch and along with pulmonary artery.Any failure of
ductus arteriosus to close after birth leads to a diseased condition called
patent ductus arteriosus. The complications include pulmonary hypertension and
congestive heart failure.