This is the unknown function of the appendix in the human body

You may have heard that astronauts have their appendix removed before leaving Earth. After all, you can live without it because it's a useless organ... Or maybe not? Is there any truth to this suspicion?

Let's start by establishing the context. The appendix is ​​a small, finger-shaped pouch located where the small intestine joins the large intestine, in the cecum. Inflammation and infection of the appendix, called appendicitis , can lead to rupture of the organ and subsequent widespread infection (peritonitis), and can even be life-threatening if left untreated.

On some remote and isolated long-duration missions, such as those to Antarctica, participants have been required to undergo appendectomy before departure. This was justified by the limited access to medical facilities and the difficulties in evacuating people in these remote areas in the event of a medical emergency.

By removing the appendix before departure, the risk of appendicitis and the complications it can cause during the mission is eliminated, thus helping to ensure the safety and well-being of all involved. Apparently, it was all advantages.

In our ancestors, the appendix probably served a digestive function adapted to a diet rich in raw plants and cellulose, as it does in many modern herbivorous mammals. Thousands of years ago, it would have functioned as a functional extension of the cecum, involved in the bacterial digestion of fibrous plant materials.

As the human diet diversified and became richer in animal protein and more easily digestible cooked or fermented foods, the need for a voluminous cecum and a functional appendix to digest cellulose diminished. As a result, the human appendix shrank in size and lost its original digestive function . Because of this, it has long been considered a vestigial organ, a part of the body that was once useful but that we could now do without.

However, it is now known that, although it has lost its original digestive function, the appendix has evolved into new functions essential for human health.

Specifically, it has been shown to be an important component of immune function , particularly in the first years of life. It acts as a lymphoid organ, similar to the Peyer's patches in the gut, which contributes to the maturation of B lymphocytes (a type of white blood cell) and the production of antibodies (immunoglobulin A, to be exact), crucial for controlling the density and quality of the gut microbiota.

Furthermore, the appendix contains a highly diverse and varied microbiota , including bacteria such as Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Fusobacteria. This diversity is distinct from that of other parts of the gastrointestinal tract, suggesting a specialized role.

Appendix removal has been associated with a reduction in gut bacterial diversity. Individuals who have undergone an appendectomy show a lower abundance of beneficial short-chain fatty acid-producing bacteria , such as Roseburia, Barnesiella, Butyricicoccus, Odoribacter, and Butyricimonas. This reduction in microbial diversity can lead to gut dysbiosis and potentially increase susceptibility to various diseases.

To top it all off, appendectomy has also been linked to an increase in fungal diversity in the gut. This shift in the microbial ecosystem suggests that the appendix may also play a role in the balance between bacterial and fungal populations. This organ could act as a reservoir or storage for commensal gut microbiota, helping to repopulate the colon after exposure to pathogens or antibiotic treatment.

The appendix may also play a role in protecting the gastrointestinal tract from invading pathogens. This would explain why surgical removal of the appendix has been associated with a worse prognosis for recurrent Clostridioides difficile infection and an increased risk of inflammatory bowel disease or ulcerative colitis .

It could even be linked to the higher incidence of other conditions such as heart disease and Parkinson's disease. Therefore, the appendix's role in maintaining microbial diversity is likely critical to overall health.

Although appendix removal was relatively routine until recently, in light of the current situation, it is important to consider the potential risks associated with the procedure.

On the one hand, there are the surgical risks. Postoperative infections are a potential risk factor in any surgical procedure, and appendectomies are no exception. Hemorrhage is another potential complication that can arise during or after removal. In rare cases, postoperative bleeding may require blood transfusions. Furthermore, an appendectomy is usually performed under general anesthesia, which carries additional risks.

But, as we have just seen, the human intestinal appendix plays a significant role in regulating the intestinal microbiota, contributing to its diversity. That's why its removal is no longer recommended for astronauts as a preventative measure . NASA is aware that the potential risks associated with this intervention outweigh its benefits, and prefers to focus on maintaining astronauts' overall health and providing them with the necessary medical support during space missions.

This article was originally published on The Conversation .