Coloured 3D computed tomography (CT) scan of a healthy heart. The heart is a hollow sac of muscular tissue that pumps blood around the body. The aorta (red, centre right) carries blood to the body. To the left of the aorta is the upper part of the vena cava vein (large vessel, blue). The heart has been rotated to better show the coronary sinus (smaller blue vessel at centre) on the wall (transparent) of the heart. It is responsible for delivering deoxygenated blood from the heart muscle to the right side of the heart. The coronary sinus is drained into by several smaller cardiac veins (even smaller vessels, blue). To the left of the coronary sinus on the heart wall is the circumflex artery (smaller red vessel).