Embryo

Question 1

What are the 4 main regions of the heart present during the 4th week of development?

Answer 1

• Truncus
• Bulbis Cordis
• Primitive ventricle
• Primitive atria

(Conus)

Question 2

How does the orientation of these regions shift during heart looping?

Answer 2

First: in a cardiac tube — Truncus, bulbus cordis, primitive ventricle, primitive atria (grows longitudinally)

• Heart loops to the right of the embryo (D-loop)
• Primitive atria rotate posteriorly
• • Long axis of atrioventricular canal