Session 3.2

Question 1

How many days after fertilisation does cv circulation begin?

Answer 1

22 days

Question 2

What is needed to develop the 4 chambers?

Answer 2

Septation

• interatrial
• interventricular
• separation of ventricular outflow trunk, both pulmonary and aortic

To create the 4 chambers

Question 3

What is the first step of septation?

Answer 3

• endocardial cushions develop in the atrioventricular region
• divides heart into right and left channels

Question 4

How does atrial septation occur?

Answer 4

• septum primum grows towards fused endocardial cushions
• ostium primula is the hole present before septum premium fuses cushions (allows blood to flow between atria)
• before ostium primum closes, a second hole, the ostium second I’m appears in the septum primum
• a second cresent shaped septum, the septum seconded grows, with a hole in it - the foramen ovale.

Question 5

What are the relative pressures in the atria in utero??

Answer 5

Right atrial pressure is greater than LA pressure as oxygenated blood from the placenta arrives to the RA via the umbilical vein draining into the IVC

Question 6

What causes the foramen ovale to close?

Answer 6

Pressure in LA> pressure in RA, septum primum pushed against septum Secunderabad so blood cant flow through

Question 7

What are the remnants of the foramen ovale and the ductus arteriosus?

Answer 7

Fossa ovalis and ligamentum arteriosum

Question 8

What is hypoplastic left heart syndrome?

Answer 8

• under formed left heart
• defect in developement of mitral and aortic valves, resulting in atresia and limited flow
• ostium seundum too small, therefore fight go left flow is inadequate in utero
• left heart is therefore underdeveloped as low blood flow in chamber

Question 9

How does ventricular septation occur?

Answer 9

• ventricular septum forms which has 2 components, muscular and membranous
• muscular portion forms most of the septum and grows upwards towards the fused endocardial cushions

Question 10

How does the primary intraventricular foramen develop?

Answer 10

Muscular option grows upwards towards endocardial cushions forming small gap. (Atrioventricular canal)

Question 11

How does the primary intraventricular foramen close?

Answer 11

Membranous portion of the septum formed by connective tissue derived from endocardial cushions fill the gap

Question 12

Where is ventricular septal defect most common?

Answer 12

In the membranous portion of the intraventricular septum (failure in formation)

Question 13

How do endocardial cushions grow in the truncus arteriosus?

Answer 13

As they grow towards each other they twist around each other = form a wedge of tissue and thus a spiral septum

Question 14

What is tetralogy of fallot?

Answer 14

• ventricular septal defect
• overriding aorta
• RV outflow tract obstruction
• RV hypertrophy
• conotruncal septum formation defective