CVS Session 3 (Lecture 3.1)

Question 1

Which 3 septa are created during septation?

Answer 1

1) Interatrial
2) Interventricular
3) Ventricular outflow tracts separating aorta and pulmonary trunk

Question 2

After looping, by what structure does the atrium communicate with the ventricle?

Answer 2

Atrioventricular canal

Question 3

Describe the first step of septation.

Answer 3

Expansions in the dorsal and ventral walls cause the production of endocardial cushions in the AV region.
They divide the heart into right and left channels.

Question 4

Describe atrial septation (4 steps).

Answer 4

1) Septum primum grows down towards the fused endocardial cushions
2) Ostium primum is the hole present before septum primum fuses with the endocardial cushions
3) Before the O.P. closes, a second hole, the ostium secundum appears in septum primum
4) A second crescent shaped septum, the septum secundum grows; the hole in the septum secundum is the foramen ovale.

Question 5

Where are the left and right auricles derived from?

Answer 5

Primitive atrium

Question 6

What does the RA absorb?

Answer 6

Sinus venosus

Question 7

What does the LA sprout and absorb?

Answer 7

Sprouts PV, grows and absorbs it + first 4 branches

Question 8

What is the adult remnant of the shunt used to bypass the lungs?

Answer 8

Fossa ovalis (from foramen ovale) in RA

Question 9

What are the two components of the ventricular septum?

Answer 9

Muscular and membranous

Question 10

Describe ventricular septation.

Answer 10

1) Muscular portion forms most of the septum and grows upwards towards the fused endocardial cushions.

Question 11

What is the name of the small gap left by the upward growth of the muscular portion of the ventricular septum?

Answer 11

Primary interventricular foramen.

Question 12

How is the PIF closed?

Answer 12

Membranous portion of the interventricular septum formed by CT derived from endocardial cushions.

Question 13

How is the outflow tract separated?

Answer 13

Endocardial cushions appear in the TA and grow and twist around each other forming a spiral septum - conotruncal septum

Question 14

What happens when the fetus takes its first breath in regards to circulation?

Answer 14

1) Respiration begins
2) LA pressure increases so foramen ovale closes as it increases above RA pressure (RA<LA).
3) DA contracts
4) After birth DV closes with placental support removed.

Question 15

Why does the foramen ovale close?

Answer 15

RA<LA pressure so septum primum pushed against septum secundum closing FO

Question 16

What do the foramen ovale, ductus arteriosus, ductus venosus and umbilical vein turn into in the adult?

Answer 16

1) FO&raquo_space;> Fossa ovalis
2) DA&raquo_space;> Ligamentum arteriosum
3) DV&raquo_space;> Ligamentum venosum
4) Umbilical vein&raquo_space;> Ligamentum teres (hepatis)

Question 17

What doe the different parts of the bulbis cordis change into?

Answer 17

1) Proximal 1/3 = RV (trabeculated)
2) Conus cordis = outflow tract of L+RVs
3) TA = Roots + proximal aorta & pulmonary trunk