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Even after over 500 years of examination, the appendix remains one of the most enigmatic parts of the human body. Here’s what we’ve learned so far about this elusive organ.
1. THE ANCIENT EGYPTIANS REFERRED TO IT AS THE "WORM" OF THE BOWELS.
The human appendix is small, tubular, and pliable, which led the ancient Egyptians, who discovered it during embalming rituals, to liken it to a worm. To this day, medical literature occasionally describes the organ as vermiform, a term derived from the Latin word for "worm-like."
2. THE APPENDIX APPEARS IN LEONARDO DA VINCI’S SKETCHES.
The first recorded account of the human appendix came from Renaissance physician-anatomist Jacopo Berengario da Carpi in 1521. However, it's believed that Leonardo da Vinci created the earliest drawing of the organ in 1492, as part of his anatomical studies. Da Vinci claimed to have dissected 30 human bodies in his quest to understand the body’s mechanics and physiology.
3. IT'S ROUGHLY THE SIZE OF A PINKY FINGER.
The appendix is a small, tube-like structure attached to the cecum, which is the start of the large intestine in the lower right side of the abdomen. The cecum’s role is to receive undigested food from the small intestine, absorb leftover fluids and salts, and combine them with mucus for easier excretion. According to Mohamad Abouzeid, M.D., assistant professor and surgeon at NYU Langone Health, the cecum and appendix share similar tissue types.
4. CHARLES DARWIN BELIEVED IT WAS A REMNANT ORGAN…
The appendix has long been unfairly labeled a vestigial organ—an outdated notion suggesting it evolved without any real function. Charles Darwin is partly to blame for this. In the mid-19th century, the appendix had only been found in humans and great apes. Darwin theorized that our distant ancestors primarily ate plant-based diets and needed a large cecum to break down tough plant fibers. Over time, as humans and apes shifted to a more varied and digestible diet, the cecum shrank. Darwin believed the appendix was a leftover feature that emerged from the shrinking cecum, without any clear purpose.
5. … BUT THE APPENDIX MAY HAVE EVOLVED TO SUPPORT IMMUNE FUNCTION.
The appendix's location and its similar tissue structure to the cecum suggest that it may play a role in digestion. However, there's one key difference visible only under a microscope: the appendix contains a higher concentration of immune cells in its walls. “[The appendix] has a high concentration of immune cells within its walls,” says Abouzeid to Mytour.
Recent studies have linked the appendix to immune system functions, presenting a number of possible explanations. A 2015 study published in Nature Immunology by Australian researchers found that a type of immune cell called innate lymphoid cells (ILCs) thrive in the appendix. These cells appear to help repopulate the beneficial bacteria in the gut, which is crucial for recovery after infections that can deplete fluids, nutrients, and good bacteria.
A 2013 study exploring the evolutionary purpose of the appendix in various mammal species concluded that the organ evolved independently in at least 32 different lineages, but not in direct response to diet or environmental changes. This research was conducted by teams from Midwestern University and Duke University Medical Center.
In a 2017 study, the same team of researchers examined 533 mammal species and discovered that those with appendices also had more lymphatic (immune) tissue in their cecum. This observation led them to propose that the appendix might function as "a secondary immune organ." They further suggested that lymphatic tissue could help promote the growth of beneficial gut bacteria, providing additional support for the theory that the appendix serves as a ‘safe house’ for helpful gut bacteria. This bacteria plays a vital role in replenishing healthy gut flora after an infection or illness.
6. ABOUT 7 PERCENT OF AMERICANS WILL EXPERIENCE APPENDICITIS AT SOME POINT IN THEIR LIVES.
Despite being a small organ, the appendix is surprisingly prone to infection. Appendicitis occurs when the appendix becomes blocked by hardened feces (known as a fecalith or appendicolith), excess mucus, or a buildup of immune cells after a viral or bacterial infection. In the U.S., the lifetime risk of developing appendicitis is one in 15, with incidence rates rising in newly industrialized countries. It typically affects young adults and is most dangerous in the elderly.
When the appendix becomes infected, it swells as pus accumulates inside. It can expand to several times its normal 3-inch size: In 2004, an inflamed appendix removed from a British man measured over 8 inches, and in a 2007 report in the Journal of Clinical Pathology, another specimen was found to be 8.6 inches long. People with appendicitis often feel general pain around the belly button, which later intensifies on the right side of the abdomen, accompanied by nausea, vomiting, fever, or body aches. Some individuals may also experience diarrhea.
7. APPENDECTOMIES ARE NEARLY 100 PERCENT EFFECTIVE IN TREATING APPENDICITIS.
There are two primary treatments for appendicitis: appendectomy, which is the surgical removal of the appendix, or the use of antibiotics to address the underlying infection. Appendectomies boast a success rate of over 99 percent in preventing recurrent infections, as the appendix is completely removed. However, in rare cases of "stump appendicitis"—where a portion of the appendix remains and becomes infected—further surgery may be required.
Research shows that antibiotics have an initial success rate of around 72 percent. “However, when these patients are monitored for about a year, they often experience recurrent appendicitis,” says Abouzeid. A 2017 study published in the World Journal of Surgery followed 710 patients who had received antibiotic treatment for appendicitis and found that 26.5 percent experienced a recurrence of the infection within a year.
8. AN INFECTED APPENDIX DOESN’T ACTUALLY EXPLODE.
While you might picture a ruptured appendix as a dramatic event, similar to the “chestbuster” scene from Alien, Abouzeid notes that it’s not as extreme, though still dangerous. When the appendix becomes obstructed, pressure builds up within the organ, cutting off blood supply to certain areas. “The tissue dies off and breaks down, leading to perforation,” Abouzeid explains. Rather than exploding, the appendix leaks fluids that can spread infection to nearby tissues.
A ruptured appendix is a medical emergency. Sometimes, the body can contain the infection in an abscess, which can be identified through CT scans or X-rays and treated with IV antibiotics. However, if left untreated, the infection can spread to the abdominal cavity, leading to peritonitis, a severe condition that can be life-threatening.
9. SURGEONS CAN REMOVE AN APPENDIX THROUGH A SMALL INCISION.
In 1894, Charles McBurney, a surgeon at Roosevelt Hospital in New York, introduced an open-cavity, muscle-splitting technique [PDF] to remove an infected appendix, known today as an open appendectomy. Surgeons continued using McBurney's method until laparoscopic surgery became the standard. This less invasive approach involves making small incisions in the abdomen and inserting a thin tube with a camera and surgical tools. The appendix is then removed through one of these incisions, which typically measure less than an inch in length.
The first laparoscopic appendectomies were performed by German doctor Kurt Semm in the early 1980s. Since then, laparoscopic surgery has become the preferred method for treating uncomplicated appendicitis, while open appendectomies are still used for more complex cases.
10. AN APPENDIX DELAYED A ROYAL CORONATION.
In June 1902, the future King Edward VII of Great Britain developed appendicitis (referred to as "perityphlitis" at the time), just two weeks before his planned coronation on June 26. At the time, mortality rates for appendicitis were as high as 26 percent. Edward initially resisted an appendectomy, a relatively new procedure. However, renowned surgeon and appendicitis expert Frederick Treves insisted that surgery was necessary to save his life. Treves drained the infected abscess at Buckingham Palace, rather than removing the appendix, and Edward recovered in time to be crowned on August 9, 1902.
11. THE WORLD'S LONGEST APPENDIX WAS OVER 10 INCHES LONG.
On August 26, 2006, during an autopsy at a hospital in Zagreb, Croatia, surgeons removed a 10.24-inch appendix from 72-year-old Safranco August. This extraordinary specimen earned the title of the Guinness World Record for the "largest appendix removed."
