Fetal Circulation

Question 1

Throughout fetal development the maternal blood supplies the fetus with :

Answer 1

Nutrients

Placenta

Proteins

Question 2

Fetal Circulation:

What is the difference in O2 from placental blood to maternal Hgb?

How much more O2 does Fetal Hgb carry?

Answer 2

Placental Blood has a different Hgb , its O2 concentration is 50% greater than maternal Hgb, it has a greater affinity for oxygen, fetal Hgb can carry 20-30% more O2

Question 3

The roll of the Placenta :

Answer 3

1. Embryonic waste
2. Gas Exchange
3. Blood supply to the embryo, nutrients

Question 4

Fetal Circulation:

What does the umbilical vein carry to the embryo?

How is the umbilical vein travel?

Answer 4

The umbilical vein carries oxygen rich blood and nutrients from the placenta to the embryo . The umbilical vein goes through the umbilical ring / umbilicus and travels along the Abdominal wall anteriorly .

Question 5

Fetal Circulation:

What happens when circulation reaches the liver?

Answer 5

When circulation reaches the liver ½ is shunted to the liver and the other half is shunted to the IVC via the Ductus Venous. Around 80% of the blood flow is shunted from the liver

Question 6

Fetal Circulation:

Is the blood in the umbilical vein oxygenated?

What does it mix with and from where?

Answer 6

The oxygen rich blood from the umbilical vein mixes with the deoxygenated blood from the IVC ( from the lower extremities )

Question 7

Fetal Circulation:

IVC flow empties into the RA where it is shunted to the LA , through ? What ?

Answer 7

Foramen Ovale

Question 8

Fetal Circulation:

Profustion to the RV, out the PA goes where? why?

Answer 8

There is perfusion to the RV , out through the PA to the lungs for tissue perfusion and cell growth .

Question 9

Fetal Circulation:

Where is most of the volume in the PA shunted?

What does it connect?

Answer 9

Most of the volume in the PA is shunted through the Ductus Arteriosus.

This connects the PA to the AO.

Question 10

Fetal Circulation:

What is the Ductus arteriosus?

Answer 10

Ductus arteriosus - is the channel of
communication between PA and descending AO.

The RA blood (with only 52% O2) reaches RV - AP ductus arteriosus and descending aorta.

Question 11

Fetal Circulation:

Blood flow from the SVC is returning venous blood from the upper extremities this will return to the RA , to the RV , out the PA and shunted out through the ?

Answer 11

To the descending AO and bypasses perfusion to the Brain .

Question 12

Fetal Circulation:

What does the blood in the descending AO profuse?

What does it do? why?

Answer 12

In the descending Aorta the blood is partially oxygenated and will perfuse the lower regions and lower extremities. It will then return that blood flow back to the umbilical artery which leads to the placenta where gas exchanges occurs.

Question 13

New Born circulation:

What happens with inflation of the lungs?

What is the result in circulation and pressure?

Answer 13

With the inflation of the lungs , the resistance in the lungs decreases.
•As a result there is increased venous return to the right heart.
•Right heart pressures have dropped and Left heart pressures have increased.

Question 14

New born circulation:

What are the 3 fetal shunts?

What happens to the 3 fetal shunts within 48-72 hours after birth?

Answer 14

Within 48 to 72 hours the

fossa Ovalis ,

Ductus venous and the

Ductus Arterious

should close.

Question 15

New born circulation:

What does the Ductus Arterious become?

What does the umbilical vein beome?

What does the Ductus Venous become?

Where does the umbilical artery lead to?

Answer 15

The Ductus Arterious becomes the ligamentum arterious,

the umbilical vein becomes the ligamentum Teres

The Ductus Venous becomes the ligamentum venosum and

the umbilical artery leads to a umbilical ligament and the superior vesial artery.

Question 16

Answer 16

Question 17

What is the Foramen Ovale?

Answer 17

Foramen Ovale - is intracardiac
communication between RA and LA.
Venous blood drained from the upper
body of the fetus through SVC mixes
with the IVC oxygen in the placenta.
A part goes into RV - AP - ductus
arteriosus - descending aorta, and
another part passes through foramen
ovale into the LA-LV - ascending
aorta - Aortic Arch-Brain.

Question 18

What is the Placenta?

Answer 18

Placenta - is the connecting organ between mother and fetus, the most important place in
intrauterine life, performing the exchange of O2, CO2 and nutrients (glucose, amino acids,
electrolytes and water).

Question 19

What are the umbilical arteries?

Answer 19

Umbilical Arteries - are two vessels through which unoxygenated blood passes from the
descending aorta in fetal circulation to the placenta.

Question 20

What is Fetal Pulmonary circulation?

Answer 20

Fetal Pulmonary Circulation - is characterized by increased pulmonary vascular resistance,
higher than the systemic one. For this reason the RV blood shunts the lung (only a small
amount reaches the lungs), through ductus arteriosus to the descending aorta and placenta.

Question 21

What are the Umbilical vein and Ductus Venous?

Answer 21

Umbilical Vein and Ductus Venous - represent vessels linking the placenta and fetus.
Oxygenated blood from the placenta passes through the venous duct that connects with IVC
to RA. A part of oxygenated blood passes through the liver and another one by-passes the
liver to RA.

Question 22

Circulation Changes Immediately after Birth

Answer 22

Immediately after birth, at the first breath, the lungs fill with air, which replaces the fluid in
the intrauterine life. The high O2 blood level and air filling of pulmonary alveoli lead to
decreased pulmonary vascular resistance. The result is increased blood flow from the RV
toward the lungs.

Question 23

Anatomical changes Immediately after Birth

Answer 23

The umbilical cord is clamped and sectioned so that placenta is removed from the circuit.

Foramen ovale, ductus venous and ductus arteriosus arefunctionally closed.

Systemic vascular resistances increased by cutting the umbilical cord lead to functional
closure of ductus venous.
Greater pressure from LA, due to increased pulmonary blood flow, causes foramen ovale
closure.
Higher O2 blood concentration, decreased levels of prostaglandins and decreased pulmonary
vascular resistance are the factors that lead to immediate functional closure of the ductus
arteriosus.