Did you know that you have a whole new organ? The structure was actually always there, but we’re only just now recognizing what it is and how it really works. It’s a pretty big deal. It changes the way we see not only our bodies and how they work, but also a whole host of important diseases. Does that really make it a new organ, though?
An organ is a group of tissues that perform a specific function. There’s a thing in our body called the interstitium, also known as the interstitial space, which is a layer of tissue we’ve known about for a long time. It sits beneath our skin, surrounding all of our organs and arteries and veins and muscles, blanketing them on the inside just like our skin covers our body on the outside. But a few months ago, researchers were looking at a patient’s bile duct for signs of cancer when they saw something in the interstitium that didn’t match up with any known human anatomy. Up until now, we’ve thought that the interstitium was just plain ol’ connective tissue. It’s important, but pretty ubiquitous and typically not very specialized. We’ve now observed that the interstitium is actually a complex network of interconnected fluid-filled compartments, supported by connective tissue proteins like collagen and elastin.