The human appendix is a structure that is mistakenly considered vestigial given the belief that it has lost all or most of its functions through the process of evolution. The vermiform appendix is not a vestige of the blind in the ancestors of humans. The blind, who have many existing herbivores, hosts mutualist bacteria that help animals digest the cellulose found in plants. Since the human appendix does not contain a sufficient number of these bacteria, humans are no longer able to digest more than a minimal amount of cellulose daily. This interpretation is maintained even discovering some function in the human body since the vestigial organs sometimes acquire a secondary function once they lose their original function.

A possible scenario for the progression of a fully functional caecum to the human appendix was proposed by Charles Darwin. He suggested that the appendix was used to digest leaves as primates. It can be a vestigial organ, evolutionary baggage or something that ancient humans have been degrading with the course of evolution. The great blind of some herbivores, as in the horse or the koala, support this theory. The blind of the koala allows to house bacteria that help to specifically degrade cellulose. The digestive system of the ancestors of humans may have had the same function. As humans began to eat foods that were easier to digest, they became less dependent on cellulose in plants to digest energy. As the blind man became less necessary for digestion, mutations that were previously harmful were no longer important, so they could survive. These alleles became more frequent and the blind began to wane. After thousands of years, the blind man who was once needed was degraded in the current appendix. On the other hand, evolution theorists have suggested that natural selection selects long appendages because the smaller and thin ones are more susceptible to becoming inflamed and sick.

The sporadic occurrence of the appendix throughout the phylogeny might suggest that the structure evolved evolutionarily for a specific function rather than simply being a vestige of what was once an important digestive organ. This idea was confirmed by a study in which the researchers performed a detailed comparative analysis of the anatomy of primates and conclusively demonstrated that the appendix is derived from some unidentified function and is not at all a vestigial organ. It is believed that the appendix plays a role in immune function because the structure is associated with substantial lymphatic tissue. However, the specific nature of the alleged function of the appendix has never been identified and, as a result, the idea that the appendix is a vestige continues to this day.

Pathology

Appendicitis (inflammation of the appendix) is the most common pathology of the appendix. However, the appendix is also a site of multiple tumors including the carcinoid tumor, and the appendiceal mucocele, among others.

Appendicitis Clinic

Appendicitis is a condition characterized by inflammation of the appendix. The pain usually begins in the center of the abdomen, corresponding to the development of the appendix as part of the embryonic midgut. It is usually a dull pain, visceral and poorly localized. The operation to remove the appendix is an appendectomy. Without treatment, it can lead to peritonitis, followed by shock, and if it is still untreated, death.

The pain of the irritated appendix is located in the so-called McBurney’s appendicular point. The appendiceal painful point is about 1/3 of the diagonal course from the umbilicus to the right anterior superior iliac spine, approximately where the appendix is implanted with the cecum. The most representative clinical sign in the diagnosis of acute appendicitis is achieved by pressing with the hand on the point of Mc Burney, (already described) and releasing slightly the hand. This maneuver triggers a strong pain very characteristic of this pathology, (80% as a predictive factor).