CVS 3 Embryology- Development of the CVS

Question 1

What does septation create?

Answer 1

Interatrial septum, interventricular septum and sepation of ventricular outflow tract to give pulmonary trunk and aorta giving 4 chambers of heart and selective outflow

Question 2

What are the endocardial cushions developed from?

Answer 2

neural crest cells that have migrated

Question 3

Where do the endocardial cushions develop?

Answer 3

The atrioventricular region

Question 4

In the first step of septation, the endocardial cushions divide the heart into what?

Answer 4

right and left channels

Question 5

What are the two septa that divide the atria?

Answer 5

Septum primum- grows down towards fused endocardial cushions

Septum secundum-second cresent shaped septum

Question 6

What are the three holes across the septa?

Answer 6

Ostium primum- hole present before septum primum fuses with the endocardial cushions
Ostium secundum- this appears in septum primum also, before the closure of ostium primum
Foramen ovale- hole in the septum secundum

Question 7

By what process is the ostium secundum formed?

Answer 7

apoptosis

Question 8

Which holes are involved in the right to left shunt in the atria of the fetus?

Answer 8

ostium secundum(L) and foramen ovale(R)

Question 9

What feautures of the atria are derived from the primitive atrium?

Answer 9

auricles (muscular pouch area in each atrium)

Question 10

What does the right atrium absorb?

Answer 10

sinus venosus

Question 11

What does the left atrium sprout and absorb?

Answer 11

sprouts pulmonary vein then grows to absorb it and its first 4 branches

Question 12

What is the fossa ovalis?

Answer 12

Depression in the right atrial septum that is the remnant of the shunt used in utero to bypass the lungs

Question 13

What two components does the ventricular septum have?

Answer 13

muscular which forms most of septum and grows up towards the fused endocardial cushions and membranous

Question 14

What is the foramen called when the muscular portion of the heart is starting to grow up towards the fused endocardial cushions?

Answer 14

the primary interventricular foramen

Question 15

How is the primary interventricular foramen closed?

Answer 15

the gap is filled by by the membranous portion of the interventricular septum which is dervied from the endocardial cushions

Question 16

What is the septation of the outflow tract called?

Answer 16

The conotruncal septum

Question 17

How does the conotruncal septum form?

Answer 17

Endocardial cushions appear in the truncus arteriosus and grow towards each other in a spiral to form a spiral septum

Question 18

Why does the fetal circulation bypass the liver?

Answer 18

Liver greedy as has a raft of functions so uses up oxygenated blood

Question 19

Why does the fetal circulation bypass the lungs?

Answer 19

Because the lungs are high resistance and non functional

Question 20

What changes occur as soon as a baby is born?

Answer 20

Left atrial pressure increases causing the atrial foramen to close and the ductus arteriosus contracts. Ductus venosus closes

Question 21

What is the ductus venosus?

Answer 21

Shunt from umbilical vein to inferior vena cava that allows blood to bypass the liver in the fetus

Question 22

How does the foramen ovale close?

Answer 22

The two septums are pushed together when the left atrial pressure increases above that of the right and so the holes in the septums no longer align so blood cannot be passed through

Question 23

What is the fate of the foramen ovale?

Answer 23

becomes fossa ovalis

Question 24

What is the fate of the ductus arteriosus?

Answer 24

becomes ligamentum arteriosum

Question 25

What is the fate of the ductus venosus?

Answer 25

becomes ligamentum venosum

Question 26

What is the fate of the umbilical vein?

Answer 26

becomes ligamentum teres (hepatis)

Question 27

What causes transposition of the great vessels?

Answer 27

conotruncal septum not adopting spiral course

Question 28

How common are congenital heart defects?

Answer 28

Very- 6-8/1000 births

Question 29

What causes tetralogy of fallot?

Answer 29

unequal division of conus cordis