Sinus venarum

The sinus venarum (also known as the sinus of the vena cava, or sinus venarum cavarum^[1]) is the portion of the right atrium in the adult human heart^[2] where the inner surface^[3] of the right atrium is smooth,^[2][3] whereas the rest of the inner surface is rough^[3] (trabeculated^[2]) due to the presence of pectinate muscles.^[4] The sinus venarum represents the portion of the adult heart that develops from the right sinus horn of the^[1] foetal sinus venosus.^[3][1] The sinus venarum is demarcated from the rest of the right atrium by the crista terminalis (internally) and the sulcus terminalis (externally).^[4]