Two pumps side by side.
Left = Oxygenated
Right = Deoxygenated
Atrium = Thin-walled and elastic, so it stretches as it collects the blood. It has a thin muscular wall because it only has to pump blood a short distance to the ventricles.
Ventricle = It has a thicker muscular wall because it has to pump blood a longer distance to the lungs or the rest of the body.
The left ventricle has a thick muscular wall, which means it can…