Appendix

In anatomy, the appendix is a four-inch tube of tissue connected to the cecum at the start of the large intestine, located in the lower right abdomen. The appendix appears to serve no function in the modern human body, though some scientists have suggested the organ is a storage sac for healthy bacteria that can repopulate the intestines after digestive illnesses. The standard accepted view is that the appendix is a biological remnant of ancient human ancestors who ate only leaves.

The appendix can be removed from the body with no negative effects in a procedure called an appendectomy. This surgery is required in cases of appendicitis, the inflammation of the appendix. If left untreated, appendicitis can lead to a burst appendix, which can be deadly. In addition to humans, several other species have appendices, including the great apes, various other primates, wombats, opossums, and rabbits.

Background

The English biologist Charles Darwin, who notably theorized that all living species on Earth evolved from common ancestors, argued that the appendix is a vestigial organ in modern humans. Vestigial organs are structures that performed a biological function in ancestral organisms but have become obsolete through evolution. Darwin proposed that animals with appendices all had ancient ancestors that ate primarily leaves. To digest plant tissue, an animal had to have a large cecum, the pouch located at the beginning of the large intestine. The cecum contained bacteria that allowed the animal to digest the tough material.

Over many generations, as animals began eating more fruit than leaves, the cecum started shrinking, as it became less useful. Darwin argued that the appendix was one of the cecum's sections that withered with the cecum itself. As such, he concluded that the appendix was likely useless in modern humans, whose diets generally consist of much more than leaves.

The worldwide medical community's opinion of the appendix changed somewhat over the next few centuries, however. Scientists in the twenty-first century estimated that the appendix has existed for about eighty million years in many more organisms than just the humans and other great apes as proposed by Darwin. After Darwin's time, numerous other animals were shown to have an appendix or an appendix-like structure in their intestines. These included lemurs, opossums, wombats, rabbits, voles, rats, and other rodents. By observing the existence of an appendix in such a varied array of both living and extinct species, evolutionary biologists have concluded that the appendix has evolved between eighteen and thirty-eight times in the history of earthly life.

This wide distribution of the appendix among species suggests to some scientists that the appendix is not a vestigial organ of animal ancestors, as Darwin believed, but rather a still functioning organ. These scientists assert that the appendix can store healthy bacteria that ordinarily live in the gut and help animals digest food. When the animal's digestive system becomes infected with harmful bacteria, the good bacteria can rush into the appendix, where they remain until the body's immune system eliminates the infection. Once the body is healthy again, the beneficial bacteria leave the appendix and refill the intestines.

Critics of this hypothesis agree that this proposed function of the appendix appears to make biological sense. However, they claim the fact that only a select number of animal species has an appendix is problematic. If the organ were so useful in survival and evolution, more animals would have it. Nevertheless, the surgical removal of the appendix has not been shown to cause any adverse effects on the human body, leading many biologists to maintain that the organ is mostly useless.

Overview

In humans, the appendix is an approximately four-inch-long, worm-shaped tissue attached to the cecum at the start of the large intestine in the lower right abdomen. In healthy people, the appendix simply exists in this spot for life, never affecting normal biological functions. However, some people can develop appendicitis. This is the inflammation and swelling of the appendix caused by some form of blockage such as stool, a foreign object, cancer, or intestinal infections.

The most common symptoms of appendicitis include sharp pain in the lower right abdomen, nausea, vomiting, loss of appetite, abdominal swelling, and low fever. Appendicitis is a potentially life-threatening condition. Inflamed appendices can burst, leaking toxic substances into the abdominal cavity. The cavity will then inflame in a condition called peritonitis. This is essentially poisoning that almost always causes death if not treated with antibiotics or surgical drainage.

It is necessary for individuals to be examined by a doctor as soon as possible if appendicitis is suspected. The simplest medical exam for appendicitis involves the doctor inspecting the patient's abdominal area for pain. Meanwhile, a computer tomography (CT) scan takes X-rays of the abdomen and can reveal an inflamed appendix. Appendicitis can also be detected with an ultrasound, which uses sound waves to locate problems in the body, or a complete blood count, which reveals if the body is currently fighting inflammation or infection. Surgery known as an appendectomy is required in almost all cases of appendicitis. The surgeon removes the appendix from the body before it can burst and cause further internal damage.

Appendectomies can be performed in two ways. The standard method involves the surgeon making an incision in the abdomen and cutting out the appendix. The other option is a laparoscopic appendectomy, in which the surgeon makes several small incisions in the abdomen and then inserts a camera and surgical tools into the body to remove the appendix in a minimally invasive way. Laparoscopic appendectomies are intended to cause less postoperative pain. Given the minimal or nonexistent function of the appendix in modern humans, removal of the organ is not associated with any known negative side effects.

Some doctors in the twentieth and twenty-first centuries favored antibiotics over surgery as the best means of treating appendicitis. Research performed in these periods showed that some patients recovered from the condition after taking antibiotics, but these medications can only treat appendicitis caused by bacterial infections. Any other type of appendicitis requires an appendectomy, and this procedure is still regarded by the mainstream medical community as the best treatment for appendicitis.

Bibliography

"Appendectomy." Healthline, www.healthline.com/health/appendectomy#overview1. Accessed 31 May 2017.

"Appendicitis." WebMD, www.webmd.com/digestive-disorders/digestive-diseases-appendicitis#1. Accessed 31 May 2017.

Barras, Colin. "Appendix Evolved More Than 30 Times." Science, 12 Feb. 2013, www.sciencemag.org/news/2013/02/appendix-evolved-more-30-times. Accessed 31 May 2017.

Choi, Charles Q. "The Appendix: Useful and In Fact Promising." Live Science, 24 Aug. 2009, www.livescience.com/10571-appendix-fact-promising.html. Accessed 31 May 2017.

"Emergency Signs and Symptoms of Appendicitis." Healthline, www.healthline.com/health/digestive-health/appendicitis-emergency-symptoms#overview1. Accessed 31 May 2017.

"History of Medicine: the Mysterious Appendix." Columbia University Department of Surgery, columbiasurgery.org/news/2015/06/04/history-medicine-mysterious-appendix. Accessed 31 May 2017.

Hoffman, Matthew. "Picture of the Appendix." WebMD, www.webmd.com/digestive-disorders/picture-of-the-appendix. Accessed 31 May 2017.

Marks, Jay W. "Appendicitis." Medicinenet.com, www.medicinenet.com/appendicitis/article.htm. Accessed 31 May 2017.

McKie, Robin. "Is the Mystery of the Appendix Close to Being Unravelled?" The Guardian, 3 Mar. 2012, www.theguardian.com/science/2012/mar/04/appendix-store-beneficial-bacteria. Accessed 31 May 2017.