Embryology 2 - Development of the CVS

Question 1

What is the atrioventricular canal?

Answer 1

A constriction between the atrium and ventricle, making the first division between the two

Question 2

What is the first step in septation?

Answer 2

Development of endocardial cushions on dorsal and ventral sides of atrioventricular canal

Question 3

What do the endocardial cushions do?

Answer 3

Grow towards each other to divide the heart into right and left channels

Question 4

What is the septum primum?

Answer 4

Grows down towards the fused endocardial cushions

Question 5

What is the ostium primum?

Answer 5

The hole present before the septum primum fuses with the endocardial cushions

Question 6

What is the ostium secundum?

Answer 6

A hole formed in the septum primum by apoptosis before the ostium primum closes

Question 7

What is the septum secundum?

Answer 7

A crescent shapes second septum

Question 8

What is the foramen ovale?

Answer 8

A hole in the septum secundum

Question 9

What is the fossa ovalis?

Answer 9

The adult remnant of the foramen ovale

Question 10

What are the 2 components of the ventricular septum?

Answer 10

Muscular and membranous

Question 11

Which portion of the ventricular septum froms the majority?

Answer 11

Muscular

Question 12

How does the muscular portion of the septum grow?

Answer 12

Upwards towards the endocardial cushions

Question 13

What is the primary interventricular foramen?

Answer 13

The hole at the top of the muscular portion of the ventricular septum

Question 14

What is the role of the membranous portion of the septum?

Answer 14

Fills the gap to close the primary interventricular foramen

Question 15

What is the membranous portion derived from?

Answer 15

The spiral septum that grows to separate the truncus arteriosus into the outflow vessels

Question 16

Why are the lungs mostly bypassed in foetal circulation?

Answer 16

Non functional

If they receive a lot of blood during development, they will be damaged

Question 17

How does the foetus receive oxygenated blood?

Answer 17

Via the placenta and umbilical vein - bypasses the lungs and returns to the placenta via the umbilical arteries

Question 18

When does foetal circulation change to adult circulation?

Answer 18

Immediately

Question 19

Which shunts are there in the foetal circulation?

Answer 19

Ductus venosus
Foramen ovale
Ductus arteriosus

Question 20

What is the role of the ductus venosus?

Answer 20

Allows oxygenated blood to pass from the placenta into the inferior vena cava via the umbilical vein

Question 21

What is the role of the foramen ovale?

Answer 21

Allows the blood to pass from the right atrium to the left atrium

Question 22

What is the role of the ductus arteriosus?

Answer 22

Allows blood to pass from the pulmonary trunk to the aorta - bypasses the lungs

Question 23

What is the process of shunts closing on the baby’s first breath?

Answer 23

1. Huge decrease in pressure in the lungs.
2. More blood enters lungs.
3. More blood returns to left atrium.
4. Pressure in left atrium > right atrium.
5. Foramen ovale closes.
6. Ductus arteriosus contracts.
7. Placental support is removed so ductus venosus closes.

Question 24

What is the adult form of the foramen ovale?

Answer 24

Fossa ovalis

Question 25

What is the adult form of the ductus arteriosus?

Answer 25

Ligamentum arteriosum

Question 26

What is the adult form of the ductus venosus?

Answer 26

Ligamentum venosum

Question 27

What is the adult form of the umbilical vein?

Answer 27

Ligamentum teres