Nobody knows what an organ is for sure - while it is generally accepted that certain body parts such as the brain and lungs are organs, there is no consensus on exactly what an organ is or how many you have. Recent studies have argued for the promotion of certain body parts to organs, such as the tubarial glands which are found in the center of the head and help to lubricate the upper throat area. Dysphagia, or difficulty swallowing, can result from damage to these glands. Similarly, the mesentery, which runs alongside the intestines and influences how well the guts work, is also being considered as an organ. Descriptions of the mesentery were made as far back as the 1500s by Leonardo da Vinci. The depiction of the mesentery that prevailed instead of Da Vinci’s was a fragmented one proposed by Frederick Treves, a professor at the Royal College of Surgeons at the London Hospital in 1885. Treves considered it to be three separate units, each connected to a different part of the digestive tract. Despite that predominantly accepted idea, surgeons seemed to detach the entire thing when treating colon cancer, rather than just the section that anatomists described as attached to the colon. This sparked a debate about what the mesentery even looks like, which has been going on for decades. This made some people hesitant to consider it a traditional organ if it’s not one distinct structure. However, today it is fairly well accepted that the mesentery is all one thing, bringing it closer to organ-dom. It has even been proposed as a critical player in Crohn’s disease, an inflammatory bowel disease. The mesentery might become rigid and inflamed when it isn’t working properly, which could be part of how Crohn’s disease works. Treating the mesentery like an organ could help us figure out how it inflames the guts, so this idea should be considered.
The interstitium is another body part that could be considered an organ. Researchers have known about it for decades, but they didn’t give it a second thought since it is space between parts. In 2018, it was discovered that it is actually a bunch of connected fluid-filled sacs. It can act as a shock absorber, protecting the other insides if you get jostled around too vigorously, and cells might have an easier time traveling through it. While it’s reasonable to argue that a bunch of disconnected support sacs aren’t an organ, they’re worth paying attention to since they are crucial to health in other ways. Expanding our idea of what an organ is could help us learn things about ourselves we never would have with the old rigid definitions.