In school, you probably learned that organs are the body's "machines" -- they are active, serving a function, and often complex in structure. This is easy to see when we're talking about the body's "rock star" organs: the brain, heart, lungs, liver and kidneys.
But things are a little more complicated than that. (Aren't they always?) Not everyone can even agree on how many organs the body has. Is it 50? Or even more than 70? To get to that higher number, 78, you have to count all the glands, as well as parts of the body we don't think of as very active or machine-like. Take the bladder, for example. You're probably used to thinking of it as a mere holding tank, but it's classed as an organ. There are some organs you can even do without, like the spleen.
If you're nostalgic for your old health-science class, we've got a quiz for you. We'll provide a picture, and you identify the organ. We'll also provide a hint if you get stuck... which you might, even if you love biology. We get into quite a few of the glands and lesser-known organs.
Are you up to the challenge?