what is the lub sound of the heart
Heart sounds In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heartbeat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the atrioventricular valves and semilunar valves, respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S4.
Heart (symbol) The combination of the heart shape and its use within the heart metaphor developed at the end of the Middle Ages, although the shape has been used in many ancient epigraphy monuments and texts. With possible early examples or direct predecessors in the 13th to 14th century, the familiar symbol of the heart representing love developed in the 15th century, and became popular in Europe during the 16th.[1] Before the 14th century, the heart shape was not associated with the meaning of the heart metaphor. The geometric shape itself is found in much earlier sources, but in such instances does not depict a heart, but typically foliage: in examples from antiquity fig leaves, and in medieval iconography and heraldry typically the leaves of ivy and of the water-lily.