Normal development of the heart: a review of new findings

Development and formation of the heart, the central organ of the circulatory system in vertebrates, starts early during embryonic development (second week), reaching maturity during the first few postnatal months. Cardiogenesis is a highly complex process that requires the active and orderly participation of different cardiac and non-cardiac cell populations. Thus, this process is sensitive to errors that may trigger a variety of heart-development defects, called congenital heart defects, which have a worldwide incidence of 8-10/1000 live births. A good understanding of normal cardiogenesis is required for better diagnosis and treatment of congenital heart diseases. This article reviews normal cardiogenesis by comparing information from classic studies with more recent findings. Information from descriptive anatomical studies of histological sections and selective in vivo marking of chicken embryos were emphasized. In addition, the discovery of heart fields has fueled the investigation of cardiogenic events that were believed to be understood and has contributed to proposals for new models of heart development.