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appendix

appendix The appendix is more correctly known as the ‘vermiform appendix’, meaning worm-like. It is present only in man, certain anthropoid apes, and the wombat (a nocturnal, burrowing Australian marsupial). Many herbivores are provided with a comparable, but larger structure, in which bacterial breakdown of cellulose, the main constituent of cell walls in plant fibre, takes place. In man the appendix is thought to represent a vestigial organ — one that remains in diminished form after it has ceased, in evolutionary terms, to have any significant function.

The appendix is a short, blind-ended tube arising from the caecum, the first part of the large intestine, within the lower right part of the abdominal cavity. In about half the population, the appendix is ‘retrocaecal’ — behind the caecum; in most cases, it is mobile within the abdominal cavity, suspended from the rest of the bowel by a sling-like fold of tissue (a mesentery), which has the artery to the appendix running in its free edge. The appendix first appears in the fetus at about 6 weeks of development, being initially high up in the abdomen but later descending to its final position. Approximately 1 in 100 000 people are born without an appendix — and very rarely there are two. The appendix is typically 6–9 cm long, but the length varies considerably, from 2 to 30 cm; on average it is 0.5 cm longer in the male than in the female. It is longer in the child than in the adult and shrinks further after mid life. The internal diameter of the appendix is described as wide enough to admit a matchstick, but this lumen may be partially or completely obliterated after middle age. The structure of the tube is basically the same as that of the large intestine: it has an outer muscular coat lined by a much-folded lining (mucosa). It also has aggregates of lymphoid tissue within its walls, which may replace the muscle coat in places.

The appendix in man is medically important because of its propensity to become inflamed in the condition known as acute appendicitis. In this condition, the appendix becomes swollen and the wall fills with inflammatory cells. The process may be initiated by blockage with material from the bowel. If this inflammatory process is allowed to continue, the appendix will become gangrenous and perforate, leading to peritonitis. Acute appendicitis is the most common cause of intra-abdominal infection in developed countries and appendicectomy is the most commonly performed emergency surgical operation. It is less common in developing countries where the diet contains significantly more fibre than our own. In the UK, 1.9 females and 1.5 males per thousand of the population each year get acute appendicitis and have their appendix removed. At the current rate, one in every 6 or 7 people will eventually undergo appendicectomy, even though the incidence of acute appendicitis in the UK has decreased by 50% since the 1970s. The mortality from acute appendicitis has also fallen dramatically, due to a number of factors including better general nutrition, earlier presentation to hospital, and improved anaesthetics. Post- operative problems, such as wound infection, have also become rarer due to the widespread use of antibiotics before surgery. Although appendicitis can occur at any age, it is commonest between 8 and 14 years. It is rare in the elderly and in infants below the age of 2. The cardinal sign of appendicitis is abdominal pain, which is often rather vague and poorly localized initially. As the inflammatory process proceeds, however, the pain usually localizes to the right side of the lower abdomen over the site of the appendix. There is tenderness over the appendix, often accompanied by a slight fever, a facial flush, and a rapid pulse. Despite this apparently typical picture the diagnosis is often difficult to make, particularly in females in whom gynaecological problems are also common and may closely mimic appendicitis. A percentage of appendices removed prove to be normal when examined under the microscope.

The first record of what may have been appendicitis was made by Aretaios around the third century ad. Though the appendix appeared in the anatomical drawings of Leonardo da Vinci from 1492, it was not until 1521 that it was described by an Italian anatomist, Berengario da Carpi. While there is some debate as to who first removed an appendix in England, the first deliberate appendicectomy for acute appendicitis was undertaken by a gynaecologist, Robert Lawson Tait, in May 1880 in Birmingham. The patient recovered. Prior to this Claudius Amyand, physician to Queen Anne, in 1736 successfully removed an acutely inflamed appendix from inside the hernial sac of a young boy.

A. Winter, and P. J. O'Dwyer

Bibliography

Knut, H., (ed.) (1989). The illustrated history of surgery. Harold Starke, London.


See also alimentary system.

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appendix

appendix, small, worm-shaped blind tube, about 3 in. (7.6 cm) long and 1/4 in. to 1 in. (.64–2.54 cm) thick, projecting from the cecum (part of the large intestine) on the right side of the lower abdominal cavity. The structure, also called the vermiform appendix, has no function in people and is considered a vestigial remnant of some previous organ or structure, having a digestive function, that became unnecessary to people in their evolutionary progress (see digestive system). Infection of accumulated and hardened waste matter in the appendix may give rise to appendicitis, the symptoms of which are severe pain in the abdomen, nausea, vomiting, fever, abdominal tenderness, and muscle spasm. A blood count usually shows a rise in the number of white corpuscles. Appendicitis may occur at any age, although it is more prevalent in persons under 40 years of age. The danger in appendicitis is that the appendix can rupture, either spontaneously or because the patient has injudiciously been given laxatives or an enema, and that the infection can spread to the peritoneum (see peritonitis). Surgery is indicated in appendicitis, preceded and followed by antibiotic therapy.

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appendix

appendix In some Mammalia, a vermiform, cul-de-sac termination to the caecum, located close to the junction of the large and small intestines. It contains a concentration of lymphoid tissue. In herbivorous animals (e.g. Lagomorpha) whose large intestine is involved in the digestion of cellulose, the caecum and appendix are large. In most Primates it is absent and the caecum ends bluntly. In Hominoidea, the caecum is very small, but the appendix is large.

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appendix

ap·pen·dix / əˈpendiks/ • n. (pl. -di·ces / -diˌsēz/ ; -dix·es ) 1. Anat. a tube-shaped sac attached to and opening into the lower end of the large intestine in humans and some other mammals.Also called vermiform appendix. 2. a section or table of additional matter at the end of a book or document.

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appendix

appendix (vermiform appendix) A residual part of the intestinal tract, a small sac‐like process extending from the caecum, some 4–8 cm long. Acute inflammation, caused by an obstruction (appendicitis) can lead to perforation and peritonitis if surgery is not performed in time. See also gastro‐intestinal tract.

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appendix

appendix In some mammals, finger-shaped organ, c.10cm (4in) long, located near the junction of the small and large intestines, usually in the lower right part of the abdomen. It has no known function in humans but can become inflamed or infected (appendicitis).

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appendix

appendix (vermiform appendix) An outgrowth of the caecum in the alimentary canal. In humans it is a vestigial organ containing lymphatic tissue and serves no function in normal digestive processes. Appendicitis is caused by inflammation of the appendix.

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appendix

appendix (vermiform appendix) (ă-pen-diks) n. the short thin blind-ended tube, 7–10 cm long, that is attached to the end of the caecum. It has no known function in humans and is liable to become infected and inflamed (see appendicitis).

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appendix

appendix (pl. -ices, -ixes XVI. — L. appendix, -ic-, f. appendere (see prec.).
Hence appendicitis XIX.

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appendix

appendixadmix, affix, commix, fix, Hicks, intermix, MI6, mix, nix, Nyx, pix, Pnyx, prix fixe, pyx, Ricks, six, Styx, transfix, Wicks •Aquarobics • radix • appendix •crucifix • suffix • Alex • calyx •Felix, helix •kylix • Horlicks • prolix • spondulicks •hydromechanics • phoenix •Ebonics, onyx •mechatronics • sardonyx •Paralympics • semi-tropics •subtropics • Hendrix •dominatrix, matrix •administratrix • oryx • tortrix •executrix • Beatrix • cicatrix •Essex, Wessex •kinesics • coccyx • Sussex •informatics, mathematics •Dianetics • geopolitics • bioethics •cervix • astrophysics • yikes

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