Sinus venosus is formed by the union of 2 post caval veins and 1 precaval vein. The sinus venosus receives deoxygenated blood and passes it into auricle in case of fishes and into right auricle in case of amphibians and reptiles.

Also spelled sinuatrial valve. It is the valve at the opening of the embryonic sinus venosus into the primordial right atrium. The sinus venosus later develops into part of the right atrium wall, the SA node and the coronary sinus.

it receives the deoxygenated blood and passes it to auricles in fishes and to right auricle in amphibians and reptiles

sinus Venuses recives De-oxygenated blood fromtwo superior vsna cavae and one inferior vena cava and then pass this blood to right artrium