Neonatal Circulation

Question 1

Where does maternal and fetal blood exchange occur?

Answer 1

It occurs in the intervillous space via the fetal branch villi and there is no direct connection of the two blood flows.

Question 2

Where do oxygenated and unoxygenated blood go in the fetues?

Answer 2

O2 - umbilical vein

No O2 - umbilical artery

Question 3

What separates the atria?

Answer 3

Septum Primum, which grows in the 4th week

Question 4

What does the incomplete inferior extension of the atria form?

Answer 4

Ostium Primum

Question 5

What forms the foramen secundum by the time that the osmium primum has closed?

Answer 5

The fenestrations in the cephalic septum primum coalesce to form the foramen secundum.

Question 6

Describe the blood flow in the fetus.

Answer 6

Fetal Branch Villi ->
Umbilical Vein ->
Ductus Venosus ->
IVC -> 
Right Atrium ->
Foramen Ovale ->
Left Atrium ->
Left Ventricle ->
Aorta

Question 7

Describe the flow of blood to the ductus arteriosus.

Answer 7

Blood can enter the RV through the RA and the it will then enter the pulmonary artery. The lungs are not effective so it has high pressure the forces it to flow into the ductus arteriosus and enter the systemic circulation.

Question 8

Describe blood flow from the aorta.

Answer 8

Blood goes from the aorta to the umbilical arteries and enters the placenta and the fetal branch villi

Question 9

What changes occur in the RA at birth?

Answer 9

Uterine contractions and cord clamping cause a decrease in pressure in the umbilical vein and the RA.

Question 10

What changes occur in the LA at birth?

Answer 10

Uterine contractions and cord clamping raises the vascular resistance and increases left sided pressures and increases the LA pressure.

Question 11

What occurs as a result of the changes of the RA and the LA?

Answer 11

Flow across the foramen ovale is decreased as a result and presses the septum primum against the septum secundum and closes the foramen ovale.

Question 12

Describe the activation of blood flow to the lungs at birth.

Answer 12

Alveoli are opened with the first breath and the pulmonary resistance decreases allowing it to increase flow to the left atrium. Increased systemic pressure will cause decreased flow across the ductus arteriosus and bradykinin from the lungs will cause the closure of the ductus arteriosus.

Question 13

Which has a greater O2 affinity, HbF or HbA?

Answer 13

HbF

Question 14

What is the effect of 2,3-DPG on HbF?

Answer 14

HbF does not bind to 2,3-DPG so it has no effect on it.