Embryology of the Heart

Question 1

When does the development of the heart take place?

Answer 1

• between weeks 3 and 7 after fertilization

Question 2

The 1st fold of the heart tube is called the _______, and the 2nd fold is called the _______.

Answer 2

• 1st fold: C-bend

- 2nd fold: S-bend

Question 3

Arterial blood outflow occurs at the ______ of the heart tube, while venous return inflow occurs at the _______.

Answer 3

• arterial outflow occurs at top

- venous inflow occurs at bottom

Question 4

What are the three fetal shunts present in the fetal heart?

Answer 4

• ductus venosus (bypasses the liver; blood enters directly into the IVC)
• foramen ovale (hole in atrial septum)
• ductus arteriosus (bypasses the lungs)

Question 5

T or F: in fetal circulation, the pressure of the right side of the heart is usually greater than that of the left side.

Answer 5

• false!

- the two pressures are relatively equal

Question 6

What occurs when the spiral septum fails to spiral during development?

Answer 6

• transposition of the great vessels

Question 7

What occurs when the spiral septum spirals off-center during development?

Answer 7

• tetralogy of Fallot

Question 8

What are the five embryologic structures of the heart (going from the top of the heart tube to the bottom)?

Answer 8

• truncus arteriosus, bulbus cordis, primitive ventricle, primitive atria, and sinus venosus

Question 9

What does the truncus arteriosus become?

Answer 9

• the ascending aorta and the pulmonary trunk

Question 10

What does the bulbus cordis become?

Answer 10

• the SMOOTH part of the ventricles

Question 11

What does the primitive ventricle become? The primitive atria?

Answer 11

• they become the TRABECULATED part of the ventricles and atria, respectively

Question 12

What does the sinus venosus become?

Answer 12

• the left horn becomes the coronary sinus

Question 13

What do the endocardial cushions of the outflow tract develop into?

Answer 13

• the aortic and pulmonary valves

Question 14

What do the fused endocardial cushions of the atrio-ventricle canal develop into?

Answer 14

• the AV valves

Question 15

Which cells are responsible for the spiraling of the truncus arteriosus?

Answer 15

• neural crest cells

Question 16

How many embryonic aortic arches form the bifurication of the truncus arteriosus? Separately, which arch forms the aorta? The pulmonary trunk?

Answer 16

• 2 arches form the bifurication
• arch #4 forms the aorta
• arch #6 forms the pulmonary trunk

Question 17

How many septa are involved in the formation of the 4 chambers?

Answer 17

• 3

- one between the atria, one between the ventricles, and one within the truncus arteriosus