Fetal Circulation

Question 1

When is the fetal heart fully developed?

Answer 1

Usually by week 8

Question 2

List the 3 fetal shunts

Answer 2

1. Ductus Venosus
2. Foramen Ovale
3. Ductus arteriosus

Question 3

Describe the placement of ductus arteriosus and how it allows for the movement of blood

Answer 3

Ductus arteriosus is a shunt between the ascending aorta and the pulmonary trunk. It allows for oxygenated blood coming into the left ventricle from the umbilical vein to enter into the ascending aorta bypassing the lungs and into systemic circulation

Question 4

Describe the placement of the foramen ovale and how it allows for the movement of blood

Answer 4

The foramen ovale is located in the right atrium and allows for oxygenated blood to enter into the left atrium bypassing pulmonary circulation in order to reach systemic circulation faster

Question 5

Describe the placement of ductus venosus and how it allows for movement of blood

Answer 5

Allows oxygenated blood to enter from the umbilical vein to the inferior vena cava and bypass the liver d

Question 6

Describe the path of blood from the placenta to the right atrium

Answer 6

Placenta
Umbilical Vein (shunt to liver)
Ductus venosus
IVC
Right atrium

Question 7

Describe the path of blood as it goes from the right atrium to the left atrium

Answer 7

Path 1
1. Right atrium
2. Foramen ovale
3. left atrium
Path 2
1. Right atrium
2. Right ventricle
3. Pulmonary trunk
4. Lungs
5. Left atrium

Question 8

Describe how blood in the pulmonary trunk can bypass the lungs and return to the umbilical arteries

Answer 8

1. Pulmonary trunk
2. Ductus arteriosus
3. Aorta
4. System circulation
5. Umbilical arteries
6. Placenta

Question 9

Describe the path of blood in the left atrium as it returns to the placenta

Answer 9

1. Left atrium
2. left ventricle
3. aorta
4. systemic circulation
5. umbilical arteries

Question 10

What is the function of the foramen ovale?

Answer 10

Opening of the atrial septum between the right and left atria that shunts oxygen rich blood to the brain and developing body systems

Question 11

What is the function of the ductus arteriosus?

Answer 11

Connects the pulmonary artery to the aorta

Question 12

Describe the PVR of the fetus and the factors that make it

Answer 12

In utero, the PRV is high due to the lungs being filled with fluid

Question 13

What are the factors that aid in the decrease of pulmonary vascular resistance following birth?

Answer 13

1. Increasing PaO2
2. Pulmonary vasodilation
3. Prostaglandins
4. Nitric oxide
5. removal of lung fluid due to compression during birth

Question 14

What neonatal difficulties can be present at birth?

Answer 14

1. Lack of respiratory effort
2. Blockage of airways
3. Impaired lung function
4. persistent increased pulmonary vascular resistance
5. abnormal cardiac structure/function

Question 15

When does the ductus venosus close functionally?

Answer 15

the ductus venosus closes functionally at the time of the umbilical cord clamping

Question 16

When does the ductus venosus close anatomically?

Answer 16

the ductus venosus closes anatomically at 14 days

Question 16

When does the the foramen ovale close functionally?

Answer 16

within minutes of birth due to the expansion of the lungs and the decrease in PVR resulting in higher pressures in the left atrium

Question 17

When does the ductus arteriosus close functionally?

Answer 17

the ductus arteriosus closes functionally 10-15 hours after birth

Question 17

When does the ductus arteriosus close anatomically?

Answer 17

anatomic closure of the ductus venosus occurs within 2-3 months

Question 18

When measuring an infants preductal SpO2, where would you place the SpO2 monitor?

Answer 18

on the right hand

Question 19

Why is it important to measure an infants SpO2 on the right hand?

Answer 19

1. This allows for a reading of preductal blood
2. The ductus arteriosus is still open for 10-15 hours after birth and allows for blood to be mixed post ductally, by measuring the SpO2 preductally, we know what oxygen level is reaching the brain of the infant

Question 20

What vessel is considered preductal?

Answer 20

the brachiocephalic trunk