Vermiform appendix

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

In human anatomy, the vermiform appendix (or appendix, pl. appendices) is a blind ended tube connected to the cecum, from which it develops embryologically. 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 intestine and the large intestine.

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 between 7 and 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.

The appendix is located in the lower right quadrant of the abdomen, or more specifically, the right iliac fossa. Its position within the abdomen corresponds to a point on the surface known as McBurney's point (see below). While the base of the appendix is at a fairly constant location, 2 cm below the ileocaecal valve , the location of the tip of the appendix can vary from being retrocaecal (74% ) to being in the pelvis to being extraperitoneal. In rare individuals with situs inversus, the appendix may be located in the lower left side.

Function and vestigiality

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. Whether or not the appendix has a function, it is routinely removed without any notable ill effects or side effects.

Some experts believe that the appendix was used for digesting leaves as primates. Over time, we have eaten fewer vegetables and have evolved, over millions of years, for this organ to be smaller to make room for our stomach.

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.

Loren G. Martin, 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. Adenomas also (rarely) present.

Appendicitis (or epityphlitis) is a condition characterized by inflammation of the appendix. Virtually all cases of Appendicitis require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, the appendix will rupture, leading to peritonitis, then shock, and, if continued untreated, death. Pain often begins in the center of the abdomen where the lining of the stomach is irritated then moves lower right as the condition develops, it is important to note that this makes diagnoses difficult in the early stages that only an MRI can detect. Appendicitis presents as pain in the right lower quadrant with rebound tenderness. In particular, it presents at McBurney's Point, 1/3 of the way along a line drawn from the Anterior Superior Iliac Spine to the Umbilicus. Rebound tenderness is when it does not hurt to press on the point but it hurts greatly when the pressure is released, or when the skin rebounds. Typically, point (skin) pain is not present until the parietal peritoneum is inflamed as well. Fever and immune system response are also characteristic of appendicitis. It is important to see a physician if stomach pain is present.

The surgical removal of the vermiform appendix is called 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 recognized 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.

Normal Appendix with Congestion

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Appendix: Pinworms

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See also

• Homology (biology)
• McBurney's point

External links

• "The vestigiality of the human vermiform appendix: A Modern Reappraisal" -- evolutionary biology argument that the appendix is vestigial
• Template:SUNYAnatomyLabs - "Abdominal Cavity: The Cecum and the Vermiform Appendix"

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