Protein signalling in heart development Protein signalling in heart development The heart is the first functional organ in a vertebrate embryo. There are 5 stages to heart development. Specification of cardiac precursor cells: The lateral plate mesoderm delaminates to form two layers: the dorsal somatic (parietal) mesoderm and the ventral splanchnic (visceral) mesoderm. The heart precursor cells come from the two regions of the splanchnic mesoderm called the cardiogenic mesoderm. These cells can differentiate into endocardium which lines the heart chamber and valves and the myocardium which forms the musculature of the ventricles and the atria. The heart cells are specified in anterior mesoderm by
Regional function of the heart heart (also called the myocardial fibers) are arranged in a general circumferential direction in the ventricles. In the LV, the fibers will change gradually in direction from a certain longitudinal-cirumferential direction in the outer layer of the heart (epicardium) to another angulated direction almost orthogonal in the inner wall (endocardium), becoming overwhelmingly circumferential somewhere halfway in the middle of the wall. It is, therefore, perceived that measuring the strain in the circumferential direction is a good indicator of the contractility of the fibers. There are different ways to measure the regional function of the wall. It has been proposed to