Cardiogenic Fields and Heart Tube Formation

Abstract

Abstract All vertebrates go through a type of development in which a primary PLEURIPOTENTIAL FIELD of cells is established that is subdivided into organ fields as development proceeds. Heart development is initiated when bilateral CARDIOGENIC FIELDS are established in the mesodermal GERM LAYER. These cardiogenic fields become spatially and molecularly subdivided into chamber-forming regions or fields. The mode in which the bilateral fields are brought together and fuse, as well as how the chamber forming regions are established, contribute to the complexity in understanding heart tube formation. The cardiogenic fields provide the myocardium and some of the endocardium used to build the heart tube. This chapter focuses on the myocardium, although formation of the heart tube necessitates formation of an endocardial tube, and these steps are covered briefly at the end of the chapter. The endocardium as a separate entity is covered in Chapter 9. An initial heart tube forms and begins to beat to initiate circulation even though more myocardium and endocardium are added to the INFLOW AND OUTFLOW (VENOUS AND ARTERIAL, RESPECTIVELY) POLES to lengthen the tube. The final myocardium is added to the arterial and venous poles from part(s) of the cardiogenic field that does not differentiate as myocardium with the rest of the cardiogenic mesoderm to form the initial heart tube. The cells in this subdivision of the cardiogenic fields are set aside during formation of the initial myocardial heart tube and are added later to lengthen the tube.