Session 3 - Development of The CVS

Question 1

How does the primitive heart tube develop?

Answer 1

2 endocardial heart tubes fuse together to form primitive heart tube

Question 2

How does cardiac looping occur?

Answer 2

Continued growth and elongation with the confined pericardial space causes bending of the heart, forming a U shaped loop that points generally and to the right, causing the atria to be behind and above the primitive ventricles

Question 3

How does septation of the atria occur?

Answer 3

Septum primum grows 
Ostium primum forms 
Septum primum fuses with endocardial cushions 
Ostium primum closes 
Ostium secondum forms 
Septum secondum develops 
Septum secondum overlaps ostium secundum
Septum secondum fuses with endocardial cushion partially 
Foramen ovale forms

Question 4

How does foramen ovale valve work before birth?

Answer 4

Before birth valve permits right to left flow of blood from high pressure right atrium to lower pressure left atrium as septum primum moves away to allow blood flow

Question 5

How does foramen ovale valve work after birth?

Answer 5

Pressure in LA a becomes greater than RA so septum primum closes firmly against septum secundum

Question 6

How does septation of the atrioventricular canal occur?

Answer 6

Growth of superior inferior and lateral endocardial cushions

Question 7

What are the 3 fetal circulation shunts?

Answer 7

Ductus venosus
Foramen ovale
Ductus arteriosus

Question 8

What does the ductus venosus do?

Answer 8

Allows half of the blood coming from placenta to bypass liver and go directly to inferior vena cava

Question 9

What does the foramen ovale do?

Answer 9

Allows blood to flow from right atrium to left atrium and bypass the lungs

Question 10

What does the ductus arteriosus do?

Answer 10

Allows blood to flow from right ventricle into descending aorta