What is the approximate size of the heart?

The heart is approximately the size of a human fist, which gives a relatable reference for understanding its dimensions. This comparison helps to visualize the heart's size since it varies from person to person but generally fits within this range.

The heart's shape and the fact that it must fit within the thoracic cavity make this answer particularly relevant. Each person's fist size can differ, but this comparison is useful for adults, providing a standardized way to understand the heart's dimensions. In contrast, other options suggest sizes that do not accurately capture the average heart's dimensions, and they would not fit the structural needs of the heart in the human body.