An organ with a surprising amount of function
For centuries, the human appendix was considered a vestigial organ—one that had served a function in the past but is no longer necessary. Scientists were unable to identify the physiological function of this 9 cm tube connected to the cecum (a pouch located at the junction of the small and large intestines). Therefore, it was hypothesized that the appendix originated from a portion of the cecum shrinking, which gradually occurred as our distant ancestors moved from a mainly plant-based diet. This theory emerged from anatomical observations of the cecum found in herbivorous mammals: they are significantly longer than those of carnivores or omnivores like ourselves, since this pouch mainly functions as a storage space for further digestion of cellulose (long fibres found in plants).
In other words, scientists thought that evolution simply hadn’t caught up yet with the changes in our diet, and doctors have accordingly removed this otherwise troublesome structure. Indeed, because of the appendix’s long and narrow shape, bacteria inside the large intestine can become trapped inside this blind-ended tube and cause infection, resulting in a condition known as appendicitis. Appendicitis causes swelling in the inner walls of the appendix, which leads to the accumulation of pus. If left untreated, the inflamed appendix may eventually burst and spill its infectious content into the abdominal cavity, which can be fatal. Thus, appendicitis requires immediate medical attention and is usually treated by surgically removing the appendix. The fact that patients who undergo appendix removal are perfectly able to survive without it reinforces the belief that this organ is indeed a vestigial one.
However, in the course of the last decade, studies done in several American universities have suggested that the appendix actually plays an important role in maintaining a healthy microbiome in our gut. This microbiome consists of the millions of bacterial cells that populate the inside of our intestines and bowels, helping to digest the food and nutrients going through the digestive tube. The appendix has been found to house multiple strains of beneficial microbes, providing a “safe-house” for these bacteria to multiply. So, following a bout of diarrheal illness, bacteria stored in this tube would be able repopulate the colon. Even in healthy individuals, protecting and nourishing colonies of good bacteria in the gut is essential for proper digestive functions, and also for keeping colonies of potentially harmful bacteria at bay by limiting their share of resources.
The appendix has another interesting function: if a patient ever needed to undergo surgical removal of the urinary bladder, a portion of the lower colon could then be surgically remodelled into a replacement bladder. In this case, the appendix may be used as a new sphincter muscle that helps the patient retain urine. Similarly, this narrow pouch could also be fashioned into a replacement ureter that connects the bladder to the kidneys, if necessary.
Considering the recently uncovered functions of this tiny organ (which perhaps still holds surprises for researchers), it seems that evolution was wise to preserve the human appendix after all!
