In frog, the sinus venosus directly receives

In frog, the sinus venosus directly receives caval veins (vena cavae). Two precaval veins receive blood from anterior portions of the body and one postcaval vein receives blood from posterior parts of the body. All the three caval veins open into sinus venosus, a chamber found on the dorsal side of heart. It in turn opens into right atrium and pours blood into heart.