Form-ing the muscular interventricular septum fig

180Part IISystems-Based Embryology

Tricuspid orifice

Moderator band

Outflow channel
of right ventricle

Neural tube

Dorsal
aorta

Septum Formation in the Ventricles

By the end of the fourth week, the two primitive ventricles begin to expand. This is accomplished by continuous growth of the myocardium on the outside and continuous diverticulation and trabecula formation on the inside (Figs. 13.19 and 13.26).

Right
truncus
swelling