February 24, 2010 at 3:30 am #2789
ScienceDaily (Oct. 8, 2007) Long denigrated as vestigial or useless, the appendix now appears to have a reason to be as a “safe house” for the beneficial bacteria living in the human gut.
Drawing upon a series of observations and experiments, Duke University Medical Center investigators postulate that the beneficial bacteria in the appendix that aid digestion can ride out a bout of diarrhea that completely evacuates the intestines and emerge afterwards to repopulate the gut.
“While there is no smoking gun, the abundance of circumstantial evidence makes a strong case for the role of the appendix as a place where the good bacteria can live safe and undisturbed until they are needed,” said William Parker, Ph.D., assistant professor of experimental surgery, who conducted the analysis in collaboration with R. Randal Bollinger, M.D., Ph.D., Duke professor emeritus in general surgery.
The appendix is a slender two- to four-inch pouch located near the juncture of the large and small intestines. While its exact function in humans has been debated by physicians, it is known that there is immune system tissue in the appendix.
The gut is populated with different microbes that help the digestive system break down the foods we eat. In return, the gut provides nourishment and safety to the bacteria. Parker now believes that the immune system cells found in the appendix are there to protect, rather than harm, the good bacteria.
For the past ten years, Parker has been studying the interplay of these bacteria in the bowels, and in the process has documented the existence in the bowel of what is known as a biofilm. This thin and delicate layer is an amalgamation of microbes, mucous and immune system molecules living together atop of the lining the intestines.
“Our studies have indicated that the immune system protects and nourishes the colonies of microbes living in the biofilm,” Parkers explained. “By protecting these good microbes, the harmful microbes have no place to locate. We have also shown that biofilms are most pronounced in the appendix and their prevalence decreases moving away from it.”
This new function of the appendix might be envisioned if conditions in the absence of modern health care and sanitation are considered, Parker said.
“Diseases causing severe diarrhea are endemic in countries without modern health and sanitation practices, which often results in the entire contents of the bowels, including the biofilms, being flushed from the body,” Parker said. He added that the appendix’s location and position is such that it is expected to be relatively difficult for anything to enter it as the contents of the bowels are emptied.
“Once the bowel contents have left the body, the good bacteria hidden away in the appendix can emerge and repopulate the lining of the intestine before more harmful bacteria can take up residence,” Parker continued. “In industrialized societies with modern medical care and sanitation practices, the maintenance of a reserve of beneficial bacteria may not be necessary. This is consistent with the observation that removing the appendix in modern societies has no discernable negative effects.”
Several decades ago, scientists suggested that people in industrialized societies might have such a high rate of appendicitis because of the so-called “hygiene hypothesis,” Parker said. This hypothesis posits that people in “hygienic” societies have higher rates of allergy and perhaps autoimmune disease because they — and hence their immune systems — have not been as challenged during everyday life by the host of parasites or other disease-causing organisms commonly found in the environment. So when these immune systems are challenged, they can over-react.
“This over-reactive immune system may lead to the inflammation associated with appendicitis and could lead to the obstruction of the intestines that causes acute appendicitis,” Parker said. “Thus, our modern health care and sanitation practices may account not only for the lack of a need for an appendix in our society, but also for much of the problems caused by the appendix in our society.”
Parker conducted a deductive study because direct examination the appendix’s function would be difficult. Other than humans, the only mammals known to have appendices are rabbits, opossums and wombats, and their appendices are markedly different than the human appendix.
Parker’s overall research into the existence and function of biofilms is supported by the National Institutes of Health. Other Duke members of the team were Andrew Barbas, Errol Bush, and Shu Lin.
This theory appears online in the Journal of Theoretical Biology.
Adapted from materials provided by Duke University Medical Center.
March 16, 2010 at 5:06 pm #3361
FOR KIDS: WHAT THE APPENDIX IS GOOD FOR
Some body parts seem pointless but in fact have purpose By Emily Sohn Web edition : Monday, March 15th, 2010
It was a Saturday morning in 1991 when 12-year old Heather Smith woke up feeling nauseous. Spring break was just beginning, and her parents were planning to take her skiing the next day in Flagstaff, Ariz. two hours from their home in Tempe.
A stomachache was not how Smith wanted to start vacation. I was hoping I would get better, she says, So I could go ski.
As the day progressed, things worsened. A sharp pain developed in her lower right side. She couldnt swallow the soup her sister warmed up for her at lunchtime. By the time she saw a doctor later that afternoon, she was hunched over in pain.
When she learned that her appendix was infected, she didnt have much time to be afraid. She was rushed into surgery. The next morning, her appendix was gone.
It was a little scary because it happened so quickly, says Smith, now an evolutionary biologist at the Arizona College of Osteopathic Medicine at Midwestern University in Glendale, Ariz. But she has never missed her long-lost organ. In fact, the emergency left her with a lifelong fascination for a body part she no longer has.
I have always been interested in the appendix and trying to figure out why we have one, Smith says. Theres been this idea for so long that it didnt do anything.
Appendices have long been considered vestigial structures. That means we dont actually need them. The brain, heart, skin and most other organs are essential for survival. But you can live a long life without an appendix. The same goes for tonsils, wisdom teeth, body hair and other vestigial structures.
At best, according to traditional thinking, vestigial structures just take up space. At worst, they can get infected and cause all sorts of trouble. So why do we have these unnecessary body parts in the first place?
Growing evidence suggests that we have them because they arent actually unnecessary at all. Their function probably depends on where you live (and perhaps when you lived). In some parts of the world, people still need vestigial body parts. Studying where and when these features are or were useful is helping scientists make new advances in modern medicine. The work is also providing insight into the history of humankind telling scientists things about our ancestors that we didnt know before.
It may be the case with a lot of unnecessary body parts that they may have had a function in the past but we dont necessarily need that function anymore, says Smith, who ended up studying the appendix sort of by accident. That can give us insights.
The hidden point
Consider your body, and youll notice a hodgepodge of random features that might seem silly when you stop to think about them. Whats the point of fingernails, for example? Why is there hair on your toes? And whats the deal with muscles in your ears? Do we really need muscles in our ears?
Throughout history, scientists, too, have wondered about structures that dont seem to do anything useful. The appendix is a popular example. This little, worm-like pouch is about four inches long and less than half an inch wide.
The organ grows near where the long intestine meets the short intestine. The intestines are essential for digestion, but the appendix appears to just sit there.
Its a dead-end sack, says William Parker, an immunologist at Duke University in Durham, N.C. It doesnt go anywhere.
Parker didnt start out intending to study the appendix. His specialty is the immune system a collection of organs, cells and molecules that our bodies use to stay healthy. But his research led him to the appendix anyway.
Parker knew that the human body is full of tiny organisms called bacteria, which can overwhelm the immune system, cause infections and make a person sick. He also knew that some bacteria are good for human health. Among other benefits, these good bacteria help people digest food and fight off bad bacteria that cause disease.
The immune system doesnt just benefit from good bacteria, though. In the 1990s, Parker and colleagues began to figure out that the immune system also helps good bacteria flourish. These bacteria appear in thin layers called biofilms, which grow on the side of the gut near and inside the appendix. These biofilms, the researchers learned, provide a barrier that keep out bad bacteria.
Once we figured that out, it should have been obvious to us what the appendix did, says Parker, whose team also found that the appendix has a particularly robust biofilm. Its in the perfect spot to harbor bacteria out of the flow and with a thin, narrow opening. And theres a large amount of immune tissue associated with it.
After stumbling on a possible link between the immune system and the appendix, though, the scientists still had some clues to compile before being sure of the organs purpose.
Hangout for good bacteria
In 2007, Parkers team put together all the evidence they had gathered and came up with a conclusion: The appendix serves as a safe house, Parker says, a storage bin for good bacteria. If bad bacteria attack, good bacteria emerge from the appendix and come to the rescue.
Having a safe space for good bacteria should be especially useful in parts of the world that are poor and undeveloped places where people are starving, medicine is hard to come by, clean water is scarce and diarrhea can kill. In those places, Parker says, the appendix probably helps keep people alive, especially young children.
In fact, people in the developing world rarely get infected appendixes, like Smiths. Most cases of appendicitis, in fact, occur in the United States and other developed countries, where water is purified, hospitals are sterilized and medical care is easier to get.
Those trends suggest that the appendix evolved in our ancestors to maintain health in a bacteria-filled world. Today, places such as the United States might be too sterile for the appendix. When the organ has nothing do, the immune system can turn on itself, sending people to the emergency room, Parker says. Other problems, such as allergies and immune diseases, might have similar roots.
Even in ultra-clean societies, then, the appendix and other vestigial organs might be unrecognized heroes.
Just because body parts dont seem to have any usefulness here doesnt mean you wouldnt need them if you were suddenly thrown in the middle of the woods somewhere and had to drink from whatever mud hole you could find nearby and you had to run away from predators, Parker says. Problems we are having today with allergies and autoimmune diseases are a result of the body not really fitting in with our culture.
Figuring out the true purpose of the appendix and other overlooked organs, Parker adds, is an important step toward solving medical mysteries.
We want to understand how the body functions so we can work towards getting it to function normally, he says.
To do that, it can help to take an historical view. By considering what was normal a long time ago and comparing the old normal to the new normal, researchers can see how evolution has shaped our bodies over hundreds of thousands of years. That process of change over time is called evolution.
The best way to figure out how the body was designed to work, Parker says, is to look at how it was meant to work over hundreds of millions of years of evolution.
Wise beyond our years
The appendix isnt the only example of a body part with hidden powers. Wisdom teeth are another. This final set of molars usually grows in at around age 20. Today, most people get their wisdom teeth removed before the bulky molars can squeeze other teeth out of place or get infected.
Millions of years ago, though, human faces werent as flat as they are today and mouths had more room for wisdom teeth. After 20 years of life without dental care, our ancestors would have benefited from a fresh set of strong teeth that could chew and grind raw food.
As for other structures long thought to be pointless, a recent study found that the spleen stores a whole lot of immune cells. Among other roles, those cells help to repair hearts that are damaged. Tonsils, which are also removed routinely in many developed countries, probably help boost the immune system, as well, Parker says.
As they continue to find purposes for seemingly purposeless body parts, scientists are connecting our present with the past. They are also connecting the human animal with other animals on Earth.
Last year, Smith teamed up with Parker and other colleagues to look at a whole bunch of mammal species, some that lived tens of millions of years ago. The researchers found that the appendix has existed in a wide range of animals, from rodents to primates to Australian marsupials. The study also revealed that the appendix evolved more than once throughout history. Both findings suggest that the appendix has had an important purpose throughout time.
By looking closely at our bodys pointless parts, we can begin to imagine what our bodies used to be able to do. Recognizing the bodys lingering power could also open up a whole new future of possibilities.
Our evolution gives our bodies a lot of resilience and strength we really dont need very much in our society, says Parker. I sit around in my office and have all the food I want. My body can do so many things I never ask it to do.
May 8, 2011 at 4:56 am #2790
This come on the heals of other recent reports indicating that appendicitis may have causes that are directly related to microbial pathogens. Even so, the implications for people choosing to avoid having body parts removed are compelling.
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