Why appendix is ​​not as useless as believed

For centuries, the appendix — this cylindrical-shaped organ that measures about 10 cm and is connected to the first part of the large intestine — has been an enigma.

Jacopo Berengario da Carpi, an Italian physician, published the first description of the appendix in 1521, in his “Commentaria”, and described it as a small empty cavity.

Leonardo da Vinci theorized that it was a place to trap excess gas and prevent the intestines and colon from bursting during bouts of constipation.

The word “appendix” was first used by Andreas Vesalius in 1953, comparing the organ to an earthworm.

The Swiss botanist Caspar Bauhin speculated in 1579 that it was a receptacle for the feces of the fetus during pregnancy.

Without a very convincing theory, in his book on the theory of evolution, in 1871, Charles Darwin proposed the hypothesis that the appendix actually had no function: it was a remnant organ that had lost its raison d’etre “as a consequence of changes in diet or habits”.

That’s probably what you learned in school.

But in the mid-20th century, with the development of tools to look at our organs more closely, the idea that the appendix was only good for inflaming and putting lives at risk (through appendicitis) began to dissipate. .

And, in the 21st century, scientists have discovered that this organ is far from just an excess piece.

Sanctuary

In 2007, a team at Duke University Medical Center made a breakthrough when they discovered that the appendix had a rich biofilm.

It is a layer of beneficial bacteria, the ones that live in our intestines, form our flora and help extract energy and nutrients from food. Plus, when they digest fiber, they produce short-chain fatty acids that can cross into the bloodstream and protect the brain.

The mysterious and disdained organ then came to be seen as a reservoir of these bacteria, ready to repopulate the intestine when we lose them — for example, in episodes of diarrhea or ingestion of antibiotics.

This was something Darwin could never have guessed, as he lived long before science recognized the existence of the human microbiome.

And there was something else.

A few decades earlier, the appendix had been found to have a high concentration of gut-associated lymphoid tissue (Galt), but until then it was not known that this helped to stimulate the immune system in the event of an invading pathogen.

That is, in addition to serving as a storehouse for bacteria, it is involved in understanding when the gut is threatened and how to respond to danger.

Misunderstanding

Six years later, another Duke Medical Center study found that people without an appendix tend to be at increased risk of a nasty and dangerous bacterial infection: Clostridium difficileor Ç diff.

But the scientists also discovered something that took them by surprise: anti-evolutionists had taken advantage of their research.

That’s because, inadvertently, they had denied something Darwin said — and precisely in one of the most common and popular examples cited as evidence of the natural selection of species.

The researchers, the creationists claim, had demonstrated that the theory of evolution was invalid.

“Darwin was wrong (in assuming) that the appendix was vestigial,” explained Heather Smith, professor of anatomy at Midwestern University in Arizona (USA), who vehemently explains: “That doesn’t mean he was wrong about the theories of natural selection and our understanding of adaptation”.

Indeed, Smith’s own research has shown that, far from undermining the theory of evolution, the appendix confirms it.

Millions of years

In 2017, Smith and his colleagues decided to compare the human appendix with that of 533 mammal species.

Revealing a history of more than 80 million years, they built a kind of large mammal family tree, with which it is possible to map data and estimate how many times species have evolved in a particular trait — in this case, in the appendix.

“We determined that the appendix evolved around 30 times over the course of mammalian evolution, and that implies that it fulfills an important function, otherwise it would not continue to appear in evolution.”

In evolutionary terms, if an organ appears, stays, and doesn’t disappear, that’s a good indicator that it’s useful in some way. Even more so if this happens in several different mammalian lineages.

gut-brain axis

Now, the appendix is ​​the focus of studies that try to better understand its function. One, published in July 2021 by researchers at Inserm and the French Museum of Natural History and inspired by the Smith team’s large family tree, analyzed data on 258 mammal species and saw that the presence of the appendix may be related to greater longevity.

At the same time, some research suggests a connection — or axis — between the gut and the brain.

“One of the most exciting areas of brain science and neurology at the moment is the growing awareness of the gut and gut microbiota in neurodegenerative diseases,” Professor John Cryan, from the University of Cork (Ireland), an expert on the subject, tells the BBC.

Research is still ambiguous, but he said “one thing is clear: we cannot ignore the appendix when it comes to brain-gut signaling.”

Appendicitis

But there are cases where we really can’t keep our appendix.

Although a growing number of studies (among them a meta-analysis of research with 404 pediatric patients) have pointed out that, in cases of non-severe appendicitis, it is possible to treat the infection with antibiotics (in an attempt to avoid surgery to remove the appendix). ), this is still not considered a safe option.

A perforated, cancerous, or severely injured appendix is ​​a serious medical emergency with potentially life-threatening consequences, so it needs to be excised.

And not only is it proven that we can live a full and happy life without it, but none of the scientific findings indicate that appendix removal surgery has an effect on longevity.

Appendicitis in youth — treated with removal surgery — is considered beneficial, as it strengthens an education of the immune system that allows it to fight later infections efficiently.

What the recent history of this small piece of our anatomy teaches us is that the human body is extremely complex – and we still have a lot to understand.