These oddly fascinating videos show a fruit fly's heart beating. While a fruit fly's heart doesn't look anything like our own, it might just tell us a little bit about why our hearts fail.
A big, muscular heart is not as healthy as it sounds. Enlarged hearts, which have overly thick and muscular walls, decreases the volume of blood in the chambers of the heart. They force the heart to work harder in order to achieve the same amount of blood flow in a smaller and leaner heart. Humans with enlarged hearts are in danger.
And so are insects with enlarged hearts, even though their hearts look nothing like our own. Insects don't even really have a circulatory system. They have no blood vessels. Blood just squishes around the hollow places in their body. When necessary, it is forced to move from one area to another by a large central tube, which is the equivalent of a heart. It pulses regularly in order to move the insect's blood. (It doesn't just pulsate one way. Unlike human hearts, insect hearts can pulsate backwards, moving the blood both directions.)
What can an organ so unlike our own tell us about human hearts? They can give us an indication of what goes into an enlarged heart. Researchers caused a certain gene in a fruit fly to over-express itself, enlarging the fly's central tube to the point at which it was narrow, and had to pulse more rapidly to circulate the fruit fly's blood. The researchers then took out the heart (RIP, fly) and counted the cells. Regular fruit flies have 104 cells making up their hearts, while the fruit flies with the enlarged hearts also had 104 cells in their hearts. If genetically-caused enlargement of the heart works the same way, hearts don't enlarge by adding cells, they enlarge by beefing up the cells they already have.