Published June 07, 2023 by

The function of the Appendix in the Digestive System


An Introduction 

The appendix is a tube-shaped pouch located in the lower right area of the belly. It also receives other names such as: cecal appendix, vermiform appendix and vermicular appendix.

It is not considered essential for the body, but its inflammation can cause health problems.

What is the Appendix?

The appendix is a small tubular extension that ends in a blind end. Shaped like a small bag, it is about 10 cm long and connects with the first part of the large intestine.

It is located in the lower right region of the abdomen, in the cecum, which in turn is connected to the first portion of the large intestine.

What is the appendix for?

For a long time, efforts were made to understand the function of the appendix in the body, in which it was believed that the appendix would be a vestigial organ, that is, that with evolution they became out of use due to adaptation to new lifestyles, different of the most primitive ancestors.

Theories that explain the function of the human appendix Despite contrary evidence, based on studies of comparative anatomy in primates, the appendix was considered for a long time as a vestigial structure, that is, a structure that, over the course of evolution, lost its original function . Nowadays there are some theories that explain the function of the human appendix. One argues that the human appendix supports the immune system. When microscopically examining the appendix, the researchers found a significant amount of lymphoid tissue, a tissue that has an abundant amount of lymphocytes .

It is now understood that intestinal bacteria that support digestion and ward off illnesses reside in the appendix. Following investigations into the possibility that the appendix had a role in the digestion of vegetables, this result was reached.

Additionally, according to researchers, the appendix contains a significant number of lymphocytes, which are defense cells that are associated with the immune system.

However, if the appendix is removed, its absence does not cause any damage, anomaly or deficiency to the organism, this being one of the organs of the human body without which you can survive.

Appendix in Digestion

Considered a vestige without function, which only manifests itself to cause appendicitis, this small organ would in fact serve as a shelter for a bacterial flora helping us to digest food. But, in industrialized countries, indeed, this accommodation would be more harmful than useful.

In human anatomy textbooks, the vermiform appendix, or appendix, is described as a diverticulum of the cecum, at the entrance to the large intestine, from 5 to 12 centimeters, without further precision. It is then immediately associated with its inflammation, called appendicitis. In short, the only function of this appendix would be to pose a mortal risk to the individual. From an evolutionary point of view, this would be a curiosity. The understanding of its role is not facilitated by its rarity in mammals. The anatomy of the cecum varies greatly from species to species and this part of the intestine is mostly developed in herbivores.

We know that the appendix manufactures immunoglobulins, and must therefore intervene, in one way or another, in the immune system. But other parts of the body also manufacture immunoglobulins and the removal of the appendix, common in many countries, does not seem to generate complications. The cause is understood: the appendix would be a vestigial organ, a qualifier given to an atrophied anatomical structure which is only the memory of an organ present in distant ancestors.

The role of the appendix in restocking the intestinal flora

Diseases such as dysentery or cholera contaminate the intestine. The only way out is to get rid of the bad microbes. That's where diarrhea occurs. In cases of severe diarrhea, not only are the bad microbes lost, but everything inside the gut, including what is known as the biofilm (a thin, delicate layer made up of microbes, mucus, and immune system molecules) . When leakage of intestinal contents occurs, the beneficial bacteria hidden in the appendix emerge and repopulate the biofilm layer of the intestine before harmful bacteria take hold.

Should you avoid removing the appendix?

 Despite the important role proposed by the team of scientists at Duke University, one should not forget that the appendix has its villainous side. When suffering from inflammation, it can lead to obstruction of the intestines, causing acute appendicitis, which can lead to death.

Therefore, in that case, it should, yes, be removed. But don't worry, severe infections, such as cholera or dysentery, are rare in industrialized nations or regions. People who inhabit these places can live normally without the appendix.

Bacterial flora

Charles Darwin himself looked disdainfully at this outgrowth of the caecum (the first part of the colon), considering that its size and structure prevented it from participating in digestion. Error, say today researchers from Midwestern University, led by Heather Smith say the opposite: the appendix in fact plays a key role in the immune system, which confirms the hypothesis put forward in 2007, by William Parker. The ileocaecal appendix, as its full name implies, is where the bacterial flora of the body resides, claims this Duke University researcher from North Carolina. The bacterial biofilm is removed in cases of diarrhea. The reserve of the appendix then serves, in a way, to replenish the stocks.

Heather Smith's team has, this time, studied the appearance and disappearance of the appendix for 553 mammalian species that lived eleven million years ago and until today. According to her, the appendix would have evolved at least 29 times. This would prove its adaptability; this would not be linked to diets or caused by social factors. And pan on Darwin's beak!

Better still: the statistical study carried out by researchers from Midwestern University highlighted "a correlation between the presence of the appendix and the concentration of lymphoid tissue in the cecum", which "confirms the hypothesis that the appendix has an immunological function”.

Oversized Reaction

In industrialized societies, with a healthy diet and constant hygiene, this kind of indigestion is extremely rare. This is why the removal of the appendix has no effects on health. On the other hand, this role of the appendix could explain the frequency of appendicitis. The reasoning appeals to what is sometimes called the hygienist thesis. Because our modern societies expose us little to pathogenic bacteria, our bodies are ill-prepared to fight against them when we cross their path. The encounter can then more easily lead to a disproportionate reaction, causing allergies in mild cases, or inflammation against more severe attacks. This is what would happen after the intrusion of an enemy bacterium into this protected reserve that would be the appendix, causing a violent reaction and appendicitis.


Appendicitis is inflammation of the appendix and is common in children, teenagers and young adults.

Its causes are still not well understood. However, obstruction of the intestine with feces or fat is believed to result in the development of inflammation and swelling of the appendix.

With untreated appendix inflammation, it is possible for it to rupture, which can lead to a serious and life-threatening infection.