Early development of the cardiac musculature
The cardiac musculature stem from mesenchymal material that forms the cardiogenic plate in the early development before the prechordal plate (stage 8). This mesenchyme consists of a connected group of cuboid cells in the ventral mesoderm.
In stage 9 the cardiac anlage lies medio-ventral to the pericardiac coelom. Through the development of the head fold, the situation of the heart is influenced. nd now surrounds the endocardiac tube, the cardiac jelly secreted by the myocardium mantle, and the myocardium mantle itself. The myocardium mantle in stage 10 is already capable of contractions, implying a very early formation of contractive elements.
In contrast to the myoblasts of the skeletal musculature, the myocardial precursor cells do not fuse into a syncytium but rather remain as individual cells. They are connected with one another, though, by complex adhering junctions, the intercalated disks, and thus form a cellular bond that stays together.