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Vermiform appendix

Vermiform Appendix
Arteries of cecum and vermiform appendix. (Appendix visible at lower right, labeled as "vermiform process").
Normal location of the appendix relative to other organs of the digestive system (anterior view).
Latin dixermiformis
Gray's subject #942 8711
System Digestive
Precursor Midgut
MeSH Appendix
Dorlands/Elsevier a_54/12147735

In human anatomy, the vermiform appendix (or appendix, pl. appendices) is a blind ended tube connected to the cecum. It develops embryologically from the cecum. The term "vermiform" comes from Latin and means "wormlike in appearance". The cecum is the first pouch-like structure of the colon. The appendix is near the junction of the small intestines and large intestines.

Size and location

The appendix averages 100 mm in length, but can range from 20 to 200 mm. The diameter of the appendix is usually less than 7 to 8 mm. The longest appendix ever removed was that of a Pakistani man on June 11, 2003, at Pakistan Institute of Medical Sciences, Islamabad, measuring 235 mm (9.2 in) in length. [1]

While the base of the appendix is at a fairly constant location, the location of the tip of the appendix can vary from being retrocaecal to being in the pelvis to being extraperitoneal. In most people, the appendix is located at the lower right quadrant of the abdomen. In people with situs inversus, the appendix may be located in the lower left side.

Function

Medical literature shows that the appendix is not generally credited with significant function. The appendix is rich in infection-fighting lymphoid cells, suggesting that it might play a role in the immune system.[2] Whether the appendix has a function or not, it is routinely removed without any ill effects or side effects.

There have been cases of people who have been found, usually on laparoscopy or laparotomy, to have a congenital absence of their appendix. There have been no reports of impaired immune or gastrointestinal function in these people.

The most common explanation is that the appendix is a vestigial structure with no absolute purpose. In The Story of Evolution Joseph McCabe argued thus:

The vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. This interpretation of it would stand even if it were found to have a certain use in the human body. Vestigial organs are sometimes pressed into a secondary use when their original function has been lost.

The appendix is more developed in Old World monkeys.
The appendix is more developed in Old World monkeys.[3]

The appendix is thought to have descended from an organ in our distant herbivorous ancestors called the cecum (or cæcum). The cecum is maintained in modern herbivores, where it houses the bacteria that digest cellulose, a chemically tough carbohydrate that these animals could not otherwise utilize. The human appendix contains no significant number of these bacteria, and cellulose is indigestible to humans. It seems likely that the appendix lost this function before human ancestors became recognizably human.

Loren G. Martin[4], argues that the appendix has a function in fetuses and adults. Endocrine cells have been found in the appendix of 11 week old fetuses that contribute to "biological control (homeostatic) mechanisms." In adults, Martin argues that the appendix acts as a lymphatic organ.

Diseases

The most common diseases of the appendix (in humans) are appendicitis and carcinoid tumors. Appendix cancer accounts for about 1 in 200 of all gastrointestinal malignancies.

Appendicitis (or epityphlitis) is a condition characterized by inflammation of the appendix. While mild cases may resolve without treatment, most require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, mortality is high, mainly due to peritonitis and shock.

The surgical removal of the vermiform appendix is called an An appendicectomy (or appendectomy). This procedure is normally performed as an emergency procedure, when the patient is suffering from acute appendicitis. In the absence of surgical facilities, intravenous antibiotics are used to delay or avoid the onset of sepsis; it is now recognised that many cases will resolve when treated non-operatively. In some cases the appendicitis resolves completely; more often, an inflammatory mass forms around the appendix. This is a relative contraindication to surgery.

Additional images

Location of McBurney's point (#1)

The superior mesenteric artery and its branches.

The lymphatics of cecum and vermiform process from behind.

Superior ileocecal fossa.

Inferior ileocecal fossa.

Interior of the cecum and lower end of ascending colon, showing colic valve.

Lymphatics of colon.

Mucinous adenocarcinoma of the appendix tip

See also

References

  1. ^ Guinness world record for longest appendix removed.
  2. ^ Zahid, A. (2004) "The vermiform appendix: not a useless organ." J Coll Physicians Surg Pak. 14:256-258. PubMed
  3. ^ Fisher, R. E. (2000) "The primate appendix: a reassessment." Anat Rec. 261: 228-236. PubMed
  4. ^ A professor of physiology claims the appendix has a known function

External links

The content of this section is licensed under the GNU Free Documentation License (local copy). It uses material from the Wikipedia article "Vermiform appendix" modified December 8, 2007 with previous authors listed in its history.

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