Lub Dub Sound — Heart

The heart has four chambers: two upper atria (right and left) and two lower ventricles (right and left). Blood flows from the atria to the ventricles, then out to the lungs and body. The "lub-dub" corresponds to two distinct phases of the cardiac cycle:

Normal "lub-dub" sounds indicate properly functioning valves. Deviations include: lub dub sound heart