The formation of the venticular loop - the S-shaped heart

Video

The formation of the loop and the change in position of the individual cardiac segments that are connected with it can be followed by looking at the plastillin model.

Lateral view

Frontal view

The early processes of cardiac formation, in particular the forming of the loop, are very interesting from many points of view. A long, closed tube arises out of the endocardial plexus. This tubular heart largely represents the anlage for the trabeculated part of the future right and left ventricles. The outflow tract, cone and the atrium make up here only a small part.

Since the curvatures of the heart take place in various planes, the following interactive diagrams show them in two views.

The loop formation in a side view should mainly illustrate how the inflow tract (pink) slips behind the embryonic ventricle (violet) and the outflow tract (yellow). Further, the beginning formation of the sulcus atrio-ventricularis between the atrium and ventricle can be seen well (interactive diagram).

media/module16/p1g1_herzentwick10.gif — **Fig. schlaufenseitlich01 -** Formation of the cardiac loop
side-view

media/module16/p1g2_herzentwick10.gif — **Fig. schlaufenseitlich02 -** Formation of the cardiac loop
side-view

In the tubular heart the inflow tract consists on both sides of the omphalomesenteric and umbilical veins and the sinus venosus. The primordial material for the atria still lies outside the myocardiac mantle / the pericardium.

By the formation of the loop the inflow tract migrates towards the back and upwards. Thereby, more and more from the sinus venosus or the material for the atria is incorporated into the pericardial sac (pericardium). The ventricle part forms a loop towards the front and to the right = D-loop (not easily seen in this picture).

media/module16/p1g3_herzentwick10.gif — **Fig. schlaufenseitlich03 -** Formation of the cardiac loop
side-view

media/module16/p1g4_herzentwick10.gif — **Fig. schlaufenseitlich04 -** Formation of the cardiac loop
side-view

The inflow tract is now at the level of the ventricle. Through the forming of the ventricular loop a small and a large curvature comes into being. The sulcus primus corresponds to the small one. The large one is not visible in this view because it empties to the right.

The atria now enclose the outflow tract on the left and right. The ventricles grow downwards and in the middle they form an indentation, the sulcus interventricularis (not visible here). This divides it into left and right ventricles.

In the frontal view mainly the formation of the D-loop of the embryonic ventricle (violet) is easily seen. The inflow tract moves upwards and will be covered by a part of the ventricle. The development of the sulcus primus can be easily recognized in this view. Via the movement of the inflow tract to the right a part (later: right atrium) becomes visible besides the outflow tract (interactive diagram).

media/module16/p1pop_Herzfront1.gif — **Fig. 3a -** Formation of the loop
frontal view

media/module16/p1pop_Herzfront2.gif — **Fig. 3b -** Formation of the loop
frontal view

Formation of the loop, frontal view of the embryonic heart.

media/module16/p1pop_Herzfront3.gif — **Fig. 3c -** Formation of the loop
frontal view

media/module16/p1pop_Herzfront4.gif — **Fig. 3d -** Formation of the loop
frontal view

Formation of the loop, frontal view of the embryonic heart.