Terminal sulcus

The terminal sulcus of the heart is located on the external surface of a dilated heart and is a poorly defined groove that demarcates the boundary between the smooth-walled sinus venarum (derived from the embryonic sinus venosus) and the muscular right atrial appendage (the true primitive atrium). Internally, the terminal sulcus corresponds to the crista terminalis, a C-shaped muscular ridge at the ventral part of the junction of the cranial vena cava with the atrium.