lub

(noun)

The first heart tone, or S1,  caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular contraction or systole.

Related Terms

Examples of lub in the following topics:

  • Heart Sounds

    • The two major heart sounds are "lub" (from the closure of AV valves) and "dub: (from the closure of aortic and pulmonary valves).
    • This sound may be described as either a "lub" or a "dub" sound.
    • The first heart sound, called S1, makes a "lub" sound caused by the closure of the mitral and tricuspid valves as ventricular systole begins.
    • S3 makes a "ta" sound after the "lub-dub" while S4 makes a "ta" sound before the "lub-dub".
    • The closing of the heart valves generates the "lub, dub" sounds that can be heard though a stethoscope.