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
Heart from the ventricles, and the fibrous rings which serve as bases for the four heart valves. The cardiac skeleton also provides an important boundary in the heart's electrical conduction system since collagen cannot conduct electricity. The interatrial septum separates the atria and the interventricular septum separates the ventricles. The interventricular septum is much thicker than the interatrial septum, since the ventricles need to generate greater pressure when they contract. The heart has four valves, which separate its chambers. One valve lies between each atrium and ventricle, and one valve rests at the exit of each ventricle. The valves between the