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Medical literature shows that the appendix is not generally credited with significant function. The appendix is rich in infection-fighting lymphoid cells, suggesting that it might play a role in the immune system. Whether the appendix has a function or not, it can be removed without any ill effects.There have been cases of people who have been found, usually on laparoscopy or laparotomy, to have a congenital absence of their appendix. There have been no reports of impaired immune or gastrointestinal function in these people.The most common explanation is that the appendix is a vestigial structure with no current purpose. In The Story of Evolution Joseph McCabe argued thus:The vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. This interpretation of it would stand even if it were found to have a certain use in the human body. Vestigial organs are sometimes pressed into a secondary use when their original function has been lost.The appendix is thought to have descended from an organ in our distant herbivorous ancestors called the cecum (or cæcum). The cecum is maintained in modern herbivores, where it houses the bacteria that digest cellulose, a chemically tough carbohydrate that these animals could not otherwise utilize. The human appendix contains no significant number of these bacteria, and cellulose is indigestible to humans. It seems likely that the appendix lost this function before human ancestors became recognizably human.Loren G. Martin, argues that the appendix has a function in fetuses and adults. Endocrine cells have been found in the appendix of 11 week of fetuses that contribute to "biological control (homeostatic) mechanisms". In adults, Martin argues that the appendix acts as a lymphatic organ.
What is the function of the human appendix? Did it once have a purpose that has since been lost?Loren G. Martin, professor of physiology at Oklahoma State University, replies:]"For years, the appendix was credited with very little physiological function. We now know, however, that the appendix serves an important role in the fetus and in young adults. Endocrine cells appear in the appendix of the human fetus at around the 11th week of development. These endocrine cells of the fetal appendix have been shown to produce various biogenic amines and peptide hormones, compounds that assist with various biological control (homeostatic) mechanisms. There had been little prior evidence of this or any other role of the appendix in animal research, because the appendix does not exist in domestic mammals. "Among adult humans, the appendix is now thought to be involved primarily in immune functions. Lymphoid tissue begins to accumulate in the appendix shortly after birth and reaches a peak between the second and third decades of life, decreasing rapidly thereafter and practically disappearing after the age of 60. During the early years of development, however, the appendix has been shown to function as a lymphoid organ, assisting with the maturation of B lymphocytes (one variety of white blood cell) and in the production of the class of antibodies known as immunoglobulin A (IgA) antibodies. Researchers have also shown that the appendix is involved in the production of molecules that help to direct the movement of lymphocytes to various other locations in the body."In this context, the function of the appendix appears to be to expose white blood cells to the wide variety of antigens, or foreign substances, present in the gastrointestinal tract. Thus, the appendix probably helps to suppress potentially destructive humoral (blood- and lymph-borne) antibody responses while promoting local immunity. The appendix--like the tiny structures called Peyer's patches in other areas of the gastrointestinal tract--takes up antigens from the contents of the intestines and reacts to these contents. This local immune system plays a vital role in the physiological immune response and in the control of food, drug, microbial or viral antigens. The connection between these local immune reactions and inflammatory bowel diseases, as well as autoimmune reactions in which the individual's own tissues are attacked by the immune system, is currently under investigation."In the past, the appendix was often routinely removed and discarded during other abdominal surgeries to prevent any possibility of a later attack of appendicitis; the appendix is now spared in case it is needed later for reconstructive surgery if the urinary bladder is removed. In such surgery, a section of the intestine is formed into a replacement bladder, and the appendix is used to re-create a 'sphincter muscle' so that the patient remains continent (able to retain urine). In addition, the appendix has been successfully fashioned into a makeshift replacement for a diseased ureter, allowing urine to flow from the kidneys to the bladder. As a result, the appendix, once regarded as a nonfunctional tissue, is now regarded as an important 'back-up' that can be used in a variety of reconstructive surgical techniques. It is no longer routinely removed and discarded if it is healthy.Answer posted on October 21, 1999
Figure 2: Gastrointestinal tracts of various mammals. For each species, the stomach is shown at top, the small intestine at left, the caecum and associated appendix (if present) in magenta, and the large intestine at bottom right. Scale differs between species. Reproduced with modifications from Kardong 2002, p. 511. Copyright © 2002 McGraw-Hill. Throughout medical history many possible functions for the appendix have been offered, examined, and refuted, including exocrine, endocrine, and neuromuscular functions (Williams and Myers 1994, pp. 28-29). Today, a growing consensus of medical specialists holds that the most likely candidate for the function of the human appendix is as a part of the gastrointestinal immune system. Several reasonable arguments exist for suspecting that the appendix may have a function in immunity. Like the rest of the caecum in humans and other primates, the appendix is highly vascular, is lymphoid-rich, and produces immune system cells normally involved with the gut-associated lymphoid tissue (GALT) (Fisher 2000; Nagler-Anderson 2001; Neiburger et al. 1976; Somekh et al. 2000; Spencer et al. 1985). Animal models, such as the rabbit and mouse, indicate that the appendix is involved in mammalian mucosal immune function, particularly the B and T lymphocyte immune response (Craig and Cebra 1975). Animal studies provide limited evidence that the appendix may function in proper development of the immune system in young juveniles (Dasso and Howell 1997; Dasso et al. 2000; Pospisil and Mage 1998).However, contrary to what one is apt to read in anti-evolutionary literature, there is currently no evidence demonstrating that the appendix, as a separate organ, has a specific immune function in humans (Judge and Lichtenstein 2001; Dasso et al. 2000; Williams and Myers 1994, pp. 5, 26-29). To date, all experimental studies of the function of an appendix (other than routine human appendectomies) have been exclusively in rabbits and, to a lesser extent, rodents. Currently it is unclear whether the lymphoid tissue in the human appendix performs any specialized function apart from the much larger amount of lymphatic tissue already distributed throughout the gut. Most importantly with regard to vestigiality, there is no evidence from any mammal suggesting that the hominoid vermiform appendix performs functions above and beyond those of the lymphoid-rich caeca of other primates and mammals that lack distinct appendixes.As mentioned above, important differences exist in nearly all respects between the human and rabbit appendixes (Dasso et al. 2000; Williams and Myers 1994, p. 57). The rabbit appendix, for instance, is very difficult to identify as separate from the rest of its voluminous caecum (see Figure 2). Unlike the human appendix, the rabbit's appendix is extremely large, relative to the colon, and is the seat of extensive cellulose degradation due to a specialized microflora. The large rabbit appendix houses half of its GALT lymphoid tissue, whereas the contribution of the human appendix to GALT is significantly less (Dasso et al. 2000). In humans the vast majority of GALT tissue is found in hundreds of Peyer's patches coating the small intestine and in nearly 10,000 similar patches found in the large intestine. Additionally, there are important differences in lymphoid follicular structure, in T-cell distribution, and in immunoglobulin density (Dasso et al. 2000). Furthermore, from systematic analysis we know that the rabbit, rodent, and human appendixes are convergent as outgrowths and constrictions of the caecum (Shoshani and McKenna 1998). It is thus very questionable to conclude from these animal studies that the human appendix has the same function as the other non-primate appendixes.Of course, over a century of medical evidence has firmly shown that the removal of the human appendix after infancy has no obvious ill effects (apart from surgical complications, Williams and Myers 1994). Earlier reports of an association between appendectomy and certain types of cancer were artifactual (Andersen and Isager 1978; Gledovic and Radovanovic 1991; Mellemkjaer et al. 1998). In fact, congenital absence of the appendix also appears to have no discernable effect. From investigative laparoscopies for suspected appendicitis, many people have been found who completely lack an appendix from birth, apparently without any physiological detriment (Anyanwu 1994; Chevre et al. 2000; Collins 1955; Hei 2003; Host et al. 1972; Iuchtman 1993; Kalyshev et al. 1995; Manoil 1957; Pester 1965; Piquet et al. 1986; Ponomarenko and Novikova 1978; Rolff et al. 1992; Saave 1955; Shperber 1983; Tilson and Touloukian 1972; Williams and Myers 1994, p. 22).In sum, an enormous amount of medical research has centered on the human appendix, but to date the specific function of the appendix, if any, is still unclear and controversial in human physiology (Williams and Myers 1994, pp. 5, 26-29).
Errhhmm...Excuse ME !!...MY explanation carries more weight !!
Quote from: neilep on 16/03/2007 02:01:36Errhhmm...Excuse ME !!...MY explanation carries more weight !!But amateurish compared to mine!