Appendix, Rudimentary No More
The debate on the role of appendix has been going on for quite a time. While it had been discussed that appendix did have role in hindgut fermentation in animals like rabbits and some other rodents, its compete absence in other animals like cattle who depend on vegetarian diet as much was surprising at least. Its role in human beings had been furthermore relegated to a mere byproduct of evolution, whereby a once functional organ for fermentation was now believed to be vestigial. However, recent evidences had pointed otherwise.
WHAT IS AN APPENDIX?
The appendix (vermiform appendix/ cecal [or caecal] appendix/ vermix or vermiform process) is a finger-like, blind-ended tube connected to the cecum, from which it develops in the embryo. It is present only in some species of mammals. The term “vermiform” comes from Latin and means “worm-shaped.” The base of the appendix is located 2 cm beneath the junction of the large intestine and the small intestine.
WHY WAS IT CONSIDERED USELESS?
For years, the appendix was credited with very little physiological function. This was partially because of lack of research, most domesticated mammals do not have appendix, and partly because of perceived lack of any ill effects on its removal. The appendix was thought to have been an organ for fermentation on the hindgut and only useful on herbivores. The controversies for this included the fact that not all herbivores have appendix and the ancestors of man were omnivores and not strict herbivores. The presence of appendix in embryo of human was only used to support atavism (recurrence of traits of an ancestor in a subsequent generation.) Since the mammals closest to man such as dogs or cattle do not possess appendix the exact function was not appraised.
Appendicitis, the inflammation of pain is a fairly common disease in man. Called as bursting of appendix by some, it can become extremely painful, and even fatal in absence of medical treatment. These quite severe “side effects” of having an intact appendix promoted to removing the appendix at the earliest. Often, during a surgery of a completely different organ the appendix was removed so that it may not cause further troubles. Surprisingly, such an unprecedented removal of appendix did not show any ill effects. At least immediately. This further fueled the idea that appendix did not have any function.
Recent Researches and the functions of appendix:
In embryos and young adults:
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.
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.
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.
Maintain normal flora:
William Parker, Randy Bollinger, and colleagues at Duke University proposed in 2007 that the appendix serves as a haven for useful bacteria when illness flushes the bacteria from the rest of the intestines. This proposition is based on an understanding that emerged by the early 2000s of how the immune system supports the growth of beneficial intestinal bacteria, in combination with many well-known features of the appendix, including its architecture, its location just below the normal one-way flow of food and germs in the large intestine, and its association with copious amounts of immune tissue. Research performed at Winthrop–University Hospital showed that individuals without an appendix were four times as likely to have a recurrence of Clostridium difficile colitis. The appendix, therefore, may act as a “safe house” for beneficial bacteria. This reservoir of bacteria could then serve to repopulate the gut flora in the digestive system following a bout of dysentery or cholera or to boost it following a milder gastrointestinal illness.
Back up organ
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.