Fig. 2.

Mechanical forces influencing cardiac development. Inside the heart, the blood is in direct contact with the endocardium and exerts shear force on the endocardium and cyclic strain on the three heart layers. Outside the heart, the pericardial fluid generates a shear stress force on the epicardium and pericardium as well as pressure on the whole heart. The illustration shows a section of the heart wall. Arrows indicate force vectors.