Abstract
Atrioventricular septum is an organization that separates the right atrium and the left ventricle and stands between the interatrial septum and interventricular septum. The atrioventricular septum is derived from the endocardial cushion in an atrioventricular canal. When a primitive heart tube is looping, and an atrium and the ventricle become morphologically apparent, an extracellular matrix, or cardiac jelly, is remaining and increasing in an atrioventricular canal. The mesenchymal cells that were separated and transformed from the endocardial cells through a process called “epithelial-mesenchymal transformation”, invade into the cardiac jelly and form an endocardial cushion. An endocardial cushion mainly upheaves and develops from a superior part (dorsal side) and an inferior part (ventral side). The atrioventricular septum is formed of the coalescence in the central part of the superior and inferior endocardial cushion that divides an atrioventricular canal into the right (tricuspid) and left (mitral) atrioventricular valve orifice. Superior and inferior endocardium cushions extend also in the perpendicular direction to an atrioventricular canal, and participate in closing the ostium primum and formation of membranous interventricular septum. Many congenital heart diseases result from the developmental anomaly of atrioventricular septum, interventricular septum, and interatrial septum.
