Scientists discover function of human appendix

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October 9, 2007

1:28 AM

Surgeons and immunologists at the Duke University Medical School believe they have unraveled the mystery behind the function of the human appendix.

p. The organ that was once thought to be vestigial — lacking a specific function in the body — is now believed to produce and protect good bacteria in the digestive tract.

p. The gut is full of good bacteria that aid in digestion, but diseases such as cholera and amoebic dysentery can clear out these microbes.

p. It is now believed that the function of the appendix is to regenerate and store the helpful bacteria.

p. This theory is supported by the fact that food and germs pass in a one-way flow just below the large intestine.

p. In today’s society, the appendix is no longer needed because outbreaks of cholera and dysentery seldom occur, and people can repopulate their intestinal bacteria through contact with other humans.

p. The organ is thought to have been more useful centuries ago when people lived farther apart and cholera and dysentery epidemics occurred frequently.

p. Duke surgery Professor Bill Parker said that the rate of appendicitis is lower in less developed countries where the appendix is still useful in helping to protect good bacteria.
This suggests that there is a correlation between the relatively high rate of appendicitis and the lack of appendix function in developed countries.

p. According to the Center for Disease Control, 321,000 Americans were hospitalized with appendicitis in 2005.

p. Scientists and doctors have speculated for years about the possible function of the appendix. Suggestions have ranged from its playing a minor part in the gastrointestinal system to its being an organ of the immunological system.

p. In 1976, medical textbooks began to suggest that the appendix was not entirely vestigial, and that it did have a specific function — namely as an immunological mechanism.

p. The walls of the appendix contain high concentrations of lymphoid tissues, which formed the basis for the idea that the appendix played a role in the immune system. The appendix also appears to produce immune system cells.

p. Along with several other organs that contain B-lymphocyte cells, the appendix manufactures several types of antibodies, including IgA, IgM and IgG immunoglobulins. IgA immunoglobulins are vital in maintaining a protective barrier between the bowel tract and the bloodstream. IgM and IgG immunoglobulins help to fight invaders through the bloodstream.

p. The function of the appendix has often been discussed in the arguments concerning evolution. The apparent loss of function of the organ in modern society offers support for evolution of the human body, but scientific findings of modern appendix function also offer support for a non-evolutionary argument.
The appendix was even mentioned in the famous Scopes Trial concerning the teaching of evolution in schools.

p. The modern loss of appendix function appears to coincide with an increased number of appendicitis cases. Appendicitis most often occurs when the small entrance to the appendix becomes blocked.

p. This blockage results in inflammation of the appendix, which causes the symptoms of appendicitis (abdominal pain, nausea, vomiting).

p. As the inflammation continues, bacteria begins to leak out of the dying walls of the appendix and if surgical intervention does not occur, the appendix will rupture, spreading a potentially fatal infection (peritonitis) throughout the abdomen.

p. The discovery of the possible function of the appendix is monumental because it calls into question the notion of labeling organs as vestigial if they do not appear to have a function in the human body. Medical specialists like Gary Huffnagle of the University of Michigan believe theories like this may indicate that other “vestigial” organs, like tonsils, could potentially have a function.

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