Post by rizdek on May 24, 2020 9:40:57 GMT
The appendix used to be considered a vestigial organ, but this view has changed over the past decades.
Until recently, the human appendix has been regarded as a rudimentary part of the intestine. During the past few years, however, several studies have suggested its immunological importance for the development and preservation of the intestinal immune system 1. The appendix has been shown to have an important interaction with the intestinal flora 2, 3, 4. Considering the appendix as a ‘safe house’ for the commensal gut flora, these studies hypothesize that commensal bacteria can be reintroduced from the appendix in case of disease, and therefore the appendix can be considered as an important part of intestinal health. This literature review assesses the current knowledge concerning the immunological aspects of the vermiform appendix. By describing its normal physiology and the importance of its biofilm, and appraising its evolution and elucidating which aspects have changed or, more importantly, which have been preserved in the long history of its existence, a clearer understanding of its influence on the intestinal immune system will be provided.
Science? Some individuals maybe need to "get their act together then ask questions," but "science" is an approach to viewing the world and solving problems, which, among other things helped scientists who ask questions to discover that the appendix may have immunological benefits. And, fortunately, from that standpoint, it looks like the OP did have his act together. He asked a question.
Depending on what source one uses, vestigial has come to mean that much of the function, or at least the original function(s) of a given organ/adaptation is lost and/or that the current function is smaller/different than what it was thought to have been. Science is discovering that perhaps the appendix should not still be considered vestigial, however.
Using a modern approach to evolutionary biology called cladistics, which utilizes genetic information in combination with a variety of other data to evaluate biological relationships that emerge over the ages, Parker and colleagues found that the appendix has evolved at least twice, once among Australian marsupials and another time among rats, lemmings and other rodents, selected primates and humans. "We also figure that the appendix has been around for at least 80 million years, much longer than we would estimate if Darwin's ideas about the appendix were correct."
Darwin theorized that the appendix in humans and other primates was the evolutionary remains of a larger structure, called a cecum, which was used by now- extinct ancestors for digesting food. The latest study demonstrates two major problems with that idea. First, several living species, including certain lemurs, several rodents and a type of flying squirrel, still have an appendix attached to a large cecum which is used in digestion. Second, Parker says the appendix is actually quite widespread in nature. "For example, when species are divided into groups called 'families', we find that more than 70 percent of all primate and rodent groups contain species with an appendix." Darwin had thought that appendices appeared in only a small handful of animals.
"Darwin simply didn't have access to the information we have," explains Parker. "If Darwin had been aware of the species that have an appendix attached to a large cecum, and if he had known about the widespread nature of the appendix, he probably would not have thought of the appendix as a vestige of evolution."
He also was not aware that appendicitis, or inflammation of the appendix, is not due to a faulty appendix, but rather due to cultural changes associated with industrialized society and improved sanitation. "Those changes left our immune systems with too little work and too much time their hands – a recipe for trouble," says Parker.
That notion wasn't proposed until the early 1900's, and "we didn't really have a good understanding of that principle until the mid 1980's," Parker said. "Even more importantly, Darwin had no way of knowing that the function of the appendix could be rendered obsolete by cultural changes that included widespread use of sewer systems and clean drinking water."
Darwin theorized that the appendix in humans and other primates was the evolutionary remains of a larger structure, called a cecum, which was used by now- extinct ancestors for digesting food. The latest study demonstrates two major problems with that idea. First, several living species, including certain lemurs, several rodents and a type of flying squirrel, still have an appendix attached to a large cecum which is used in digestion. Second, Parker says the appendix is actually quite widespread in nature. "For example, when species are divided into groups called 'families', we find that more than 70 percent of all primate and rodent groups contain species with an appendix." Darwin had thought that appendices appeared in only a small handful of animals.
"Darwin simply didn't have access to the information we have," explains Parker. "If Darwin had been aware of the species that have an appendix attached to a large cecum, and if he had known about the widespread nature of the appendix, he probably would not have thought of the appendix as a vestige of evolution."
He also was not aware that appendicitis, or inflammation of the appendix, is not due to a faulty appendix, but rather due to cultural changes associated with industrialized society and improved sanitation. "Those changes left our immune systems with too little work and too much time their hands – a recipe for trouble," says Parker.
That notion wasn't proposed until the early 1900's, and "we didn't really have a good understanding of that principle until the mid 1980's," Parker said. "Even more importantly, Darwin had no way of knowing that the function of the appendix could be rendered obsolete by cultural changes that included widespread use of sewer systems and clean drinking water."