Is the function of the Appendix revealed?

Appendix is notorious for its inflammation (appendicitis). In order to prevent the spreading of inflammation across the abdominal cavity, inflamed appendix is usually surgically removed.

Appendix (Appendix vermiformis) is an offshoot of the colon, or more precisely, of the cecum. It can be 5 mm to 30 cm long. Cecum is located directly in the continuation of the small intestine.

It is an established opinion that appendix is a vestigial organ with no function. The belief that appendix has no function dates back to Charles Darwin, who thought that it was a throwback (unexpected detection of some physical characteristics of ancestors in descendants, which direct ancestors did not have or that were not observed).

Over time, scientists have developed assumptions that appendix actually has a function in the body and is used for the storage of “good” intestinal bacteria. Recent research by Dr. Heather F. Smith from Midwestern University in Arizona confirms this theory. Dr. Smith and her team studied the appendix in 533 species of mammals. In this research they studied whether certain species had an appendix, its size, gastrointestinal signs, environmental variables and eating habits. The collected data were entered into the phylogenetic tree, and analysis performed to study how appendix developed through the evolution of mammals and why some species have an appendix, while some do not. They found that appendix evolved independently 29 times in several separate lineages of mammals, and that it disappeared only 12 times after it has developed.

Appendix is more likely to be found in species who have tapered or spiral shaped colon, than in the species in which the colon is of the circular or cylindrical shape. They also found that the appendix had not developed independently, but as a part of the larger system which consists of the colon and the appendix. According to scientists this is compelling arguments that appendix has a function and is not a dispensable organ.

Subsequent studies in different species have shown that species which have an appendix, also have a higher concentration of innate lymphoid cells or lymphocytes, which have an important immunological role and help in the production of “good” intestinal bacteria. The above mentioned scientific research confirms that appendix is a secondary organ of the immune system, that it has an important role in storing of the “good” intestinal bacteria, and that it helps in restoring intestinal flora after some intestinal diseases, such as dysentery and cholera.

Many people live today without appendix which was surgically removed due to appendicitis. A logical question can be raised after these new scientific findings, as to whether their immune system is being compromised. Dr. Smith says that people whose appendix was surgically removed should not worry, because they may only take slightly longer to recover from the infection.

 

Sources:

  1. http://time.com/4631305/appendicitis-appendix-gut-bacteria/
  2. https://www.eurekalert.org/pub_releases/2017-01/mu-nmu010917.php
  3. https://www.sciencedaily.com/releases/2017/01/170109162333.htm
  4. https://www.researchgate.net/publication/311535700_Comptes_Rendus_Palevol_Morphological_evolution_of_the_mammalian_cecum_and_cecal_appendix_Evolution_morphologique_de_l%27appendice_du_caecum_des_mammiferes
  5. http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2009.01809.x/full