The Appendix Fights Illnesses! Seven Misunderstood Body Parts Explained.

To survive, you need your heart, lungs, and liver. But what about your appendix, tonsils, wisdom teeth, and other parts that you normally hear about only when they're being removed. Are they just troublemakers?

Not quite. "Most likely all of these were useful and all of them may still be," says Dr. Robert Ashton, a surgeon at Montefiore Medical Center who admits that "some of them are thought to be more useful than others. "

Still, some body parts may linger thanks to evolutionary laziness, says Dr. Udayan Shah, associate professor of otolaryngology at Thomas Jefferson University in Philadelphia and chair of the medical devices and drug committee for the American Academy of Otolaryngology─Head and Neck Surgery. "If it doesn't interfere with reproduction, it's not going to be removed from the human gene pool."

With recent research indicating that the appendix isn't just a ticking time bomb, we got thinking: what other body parts get an undeserved bad rap, and which ones can you live without? We found seven of the most maligned, misunderstood body parts and figured out their function (or total lack thereof). Here's the lowdown:

Appendix: For many people, it's a case of can't live with it, can live without it. In 2006, the most recent year statistics are available, 410,000 Americans had appendectomies, and suffered no shortened lifespans as a result.

Two years ago Duke University researchers proposed that the appendix─traditionally regarded as a useless, leftover "vestigial" structure─actually provided a haven where good bacteria could stay until they were needed to repopulate the gut after, say, a bad case of diarrhea. But in a study published last week in the researchers at Duke University, the University of Arizona, and Arizona State University concluded that the 80 million-year-old appendix (which sits on top of the colon) was not just the remains of a larger structure used by human ancestors to digest food.

In fact, the appendix may still help store good bacteria, but only in places where bad bacteria runs rampant, like the developing world. Humans without access to clean water supplies need the bacteria stored by the appendix to fight off illnesses like cholera.

But give the appendix nothing to do, and it can get into trouble. Researchers say the appendix only becomes inflamed when modern sewage systems and improved sanitation have left the immune system, including the appendix, bored. "We're so clean, and that causes us to get appendicitis," says immunologist William Parker, assistant professor of surgical sciences at Duke University and the senior author of the study. "Your entire immune system is hanging out, doing very little." As a result, the appendix gets swollen and bacteria inside it can start leaking out. "What medical science needs to do is figure out how to get our immune systems busy," says Parker. "An idle immune system is a devil's workshop."

Gallbladder: The gallbladder concentrates and stores bile that the body uses to break down and digest fat. But the pear-shaped sac (just below the liver) can cause pain and problems. That happens if the liquid bile contains too much cholesterol and hardens into stones in the gallbladder. "Yes, it has a use," says Montefiore's Ashton. "[But] we lead completely normal lives without it." Thanks to the liver, bile is still available, even without the gallbladder.

Spleen: In 2006, 899,000 Americans had their spleens surgically removed in a procedure called a cholecystectomy. The spleen is useful: it helps the immune system work, and the body makes blood cells there, explains Ross. The negative connotation to the word "spleen" dates back to the Middle Ages, when people believed the organ was the black-bile "humour" that caused anger. That's why, even today, people talk about getting rid of their bad mood by "venting their spleen."

Tonsils/adenoids: Part of the immune system, the tonsils are on each side of the throat and the adenoids are on top of it. But doctors often remove this lymph tissue (where both good and bad bacteria hang out) because of breathing problems such as loud snoring or because of ear and sinus problems. (It's a long tradition: the first tonsillectomy documented in Western literature dates back to a Roman surgeon in the first century.) No harm done. "Over time, children who get their tonsils or adenoids out do not have higher rates of infections," says Shah.

Tonsillectomies are controversial. In a July press conference, President Obama said, "The doctor may look at the reimbursement system and say to himself, 'You know what? I make a lot more money if I take this kid's tonsils out.' " In a press release, the American Academy of Otolaryngology─Head and Neck Surgery responded that clinical guidelines suggest that "in many cases, tonsillectomy may be a more effective treatment, and less costly, than prolonged or repeated treatments for an infected throat."

But even if people no longer need tonsils to fight infection, doctors don't just take them out prophylactically. After all, surgery can be expensive and potentially dangerous. "It's the first place the body gets exposed to foreign objects coming into the body," says Dr. Callum Ross, the anatomy course director at the University of Chicago's Pritzker School of Medicine. "There's this constant inflow of bacteria into the body through the oral cavity, so you can start making antibodies already." With any operation, there's a risk of infection and of complications, including death, from anesthesia, he says. When kids get their tonsils removed, they're usually about 5 years old. Three decades ago, 90 percent of tonsillectomies in children were performed because of recurrent infection. Today only 20 percent are for infection and 80 percent are for obstructive sleep problems, according to the American Academy of Otolaryngology. Between 1996 and 2006, the number of Americans getting tonsillectomies jumped from 418,000 to 757,000, according to the National Center for Health Statistics.

Wisdom teeth: In 2006, 39,000 Americans had their wisdom teeth (sometimes along with other teeth) removed─down from 48,000 a decade earlier. "They keep getting infected. They're difficult to get clean," explains Ross. Earlier humans needed more grinding teeth and had larger mouths before the advent of tools and cooking, which made food softer and our faces shorter and flatter. "[Today] so much of processing of food is done before it gets into our mouth," says Heather Smith, assistant professor of anatomy at Midwestern University in Glendale, Ariz., rendering these teeth redundant. For primitive man, by contrast, wisdom teeth were essential.

Uvula: People often look at the uvula in the back of their throats and think, "What the heck is that?" says Shah. But the uvula─part of the palate─helps people swallow and helps propel food downward. It redirects food so it goes down your esophagus rather than up your nose or into your trachea. It also helps with speech. Without one, people are more likely to have air escape from their nose and to have high, squeaky voices. They may even have liquid or food come out of their noses, says Shah. Because the uvula can obstruct air, doctors sometimes remove it in patients with sleep apnea. Shah recommends against piercing the uvula because of the risk of infection and speech difficulties.

Ear lobes: "No one knows why we have earlobes," says otolaryngologist D. J. Verret, a spokesman for the AAO-HNS.