Anatomy of the Child - Fetal Circulation

Question 1

Where is fetal blood oxygenated?

Answer 1

Placenta.

Question 2

What improves fetal circulation?

Answer 2

1. Ductus venosus.
2. Foramen ovale.
3. Ductus arteriosus.

Question 3

How does oxygenated blood go from the placenta into the SVC?

Answer 3

1. Placenta via left umbilical vein.
2. L) Umbilical vein joins with left branch of portal vein and goes via ductus venosus to SVC.

Question 4

Where does the ductus venosus lie?

Answer 4

Lies along the inferior surface of the liver between the attached layers of the lesser momentum.

Question 5

What happens to the ductus venosus after birth?

Answer 5

1. Blood no longer flows in the thrombosesd umbilical vein.
2. Blood in DV clots.
3. DV converted into fibrous cord - ligamentum venosum.

Question 6

Where does the ligamentum venosum lie?

Answer 6

Deep in the cleft bounding the caudate lobe of the liver.

Question 7

What happens to the intro-abdominal part of the umbilical vein?

Answer 7

Persists as fibrous cord - ligamentum teres.

Question 8

What is the connection between ligamentum venosum and teres?

Answer 8

Continuous.

Question 9

How is the inter-atrial septum different in the fetal heart compared to the adult heart?

Answer 9

It is patent - perforated by the foramen ovale.

Question 10

How does blood circulate in the heart via the foramen ovale?

Answer 10

1. Comes into the RA via IVC.
2. Goes into LA from RA via foramen ovale.

Question 11

What happens to blood when it goes through the foramen ovale in the fetal circulation?

Answer 11

The oxygenated blood bypasses the RV and the airless lungs, so goes straight into LA and eventually LV and aorta and to carotid arteries.

Question 12

What happens to the foramen ovale after birth?

Answer 12

Closed by fusion of the primary and secondary septa.

Question 13

What happens to the foramen ovale after closure ?

Answer 13

All the blood in the RA perforce passes into the RV and so to the lungs.

Question 14

How does venous blood return from the head?

Answer 14

Braciocephalic veins go to SVC.

Question 15

What happens when venous blood enters the RA from SVC?

Answer 15

There crossing of streams of the oxygenated blood (from IVC) and deoxygenated blood (SVC).

Question 16

What happens to the blood from SVC into RA?

Answer 16

1. RA into RV.
2. RV into pulmonary trunk/artery.
3. From pulmonary trunk to aorta trunk via ductus arteriosus - joins left branch of pulmonary trunk distal to origin of three aortic arches.

Question 17

What happens to the ductus arteriosus after birth?

Answer 17

Occluded by contraction of its muscular walls. Blood from RV will then go through lungs.

Question 18

What does the ductus arteriosus persist as?

Answer 18

Ligamentum arteriosum - fibrous band.

Question 19

What does the ligamentum arteriosum do?

Answer 19

Connects the commencement of left pulmonary artery to the concavity of the arch of aorta.