Formation of the Ventricles

Figure 1

In the newly formed bulboventricular loop the primitive right and left ventricles appear as expansions in the heart tube. Externally the interventricular sulcus separates the right and left ventricles and internally they are separated by the bulboventricular flange. Remember that the right ventricle arises from the proximal bulbus cordis.

• AVC = Atrioventricular canal
• BC = Bulbus Cordis
• BVF = Bulboventricular flange
• IVS = Interventricular sulcus
• RV = Right ventricle
• LV = Left ventricle

Figure 2

During the shifting of the atrioventriclar canal the proximal bulbus cordis expands forming the right ventricle. Both ventricles will continue to expand until the late 7th/early 8th week. The growth of the ventricles is due to the centrifugal growth of the myocardium and the diverticulation of the internal walls. (This is what gives the ventricle its trabeculated appearance). The muscular interventricular septum forms as a result of the expanding ventricles. The walls of the right and left ventricles grow in opposition to each other to form the muscluar septum. Thus, the septum will cease to grow when the ventriclar walls are no longer expanding.

• BC = Bulbus cordis
• IVS = Interventricular septum
• MC = Myocardium
• RV = Right ventricle