The areolar tissue located in the skin binds the outer layers of the skin to the muscles beneath. Areolar tissue is also found in or around mucous membranes, and around blood vessels, nerves, and the organs of the body.
A heart is a symbol of love. A heart shape is a symbol of love and compassion. The heart has long been used as a symbol to refer to the spiritual, emotional, moral, and in the past also intellectual core of a human being.
Probably the biggest event in the popularisation of the heart symbol, however, was when it began to be included on playing cards during the 15th century. Painters and sculptors started using the symbol more frequently, without the previous association with leaves.