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.
And this feeling is present in your very heart, because of the hormonal, neuromediatory and whatever influences your brain makes upon on it. This is the key to why heart symbol is so popular. It's symmetric aesthetically pleasing shape that looks a lot like human heart, although it's far from being exactly like it. Interestingly, because of the symbolic symmetry and division in the middle - it takes two halfs to make the whole.