Gross anatomy of the human cardiac conduction system with comparative morphological and developmental implications for human application

The main aim of this review is to provide macroscopic anatomical information on the human cardiac conduction system (CCS) with comparative morphological and developmental implications for future human application. In the elder human CCS, the sinuatrial node (SAN) is almost consistently positioned on the sulcus terminalis and is variable in size and shape with its extent. However, the atrioventricular CCS that is distal to the atrioventricular node (AVN) varies frequently in shape, size, and position with respect to some conventionally used landmarks. From the comparative anatomical viewpoint, there are marked differences between humans and most mammals and birds not only in the position of atrioventricular CCS in relation to surrounding structures but also in the morphology of the atrioventricular CCS. Therefore, experimental data obtained in most mammals and birds are difficult to apply directly to humans. Recent advances in the understanding of CCS development have been introduced for cardiologists, anatomists, and biomedical researchers. Animals whose morphology is similar to that of mature human CCS should be used for experimental and developmental research if the results are intended for human application. Research on the CCS is an exciting and progressive area, and is likely to yield solutions to a number of problems in future.