Corpus: Vermiform appendix

The vermiform appendix or appendix for short is a worm-like, approximately 10 cm long protrusion of the caecum, which consists largely of lymphatic tissue.

The appendix is localised in the lower right quadrant of the abdomen in the iliac fossa. The diameter of the organ is about 6-7 mm. The base of the appendix lies about 2 cm below the ileocecal valve. The Gerlach valve is found at the entrance, the ostium appendicis vermiformis.

The length of the appendix is very variable - it can be between 2-20 cm. The same applies to the position of the appendix in the abdominal cavity. It is most frequently found retrocaecally. It can either be located retroperitoneally or have its own mesenteric appendix (mesenteriolum).

The arterial supply is via the appendicular artery from the ileocolic artery of the superior mesenteric artery.

Position variants[Bearbeiten]

• ascending retrocaecal: approx. 64%
• descending: approx. 31%
• transverse retrocaecal: approx. 2%
• ascending paracecal: approx. 1.5%

The histological structure of the appendix essentially corresponds to the structure of the colon - however, the longitudinal musculature is not restricted to the caeca, but forms a closed layer of muscle fibres. In the mucosa of the appendix there are only crypts, no villi. The most conspicuous structure are numerous lymph follicles in the form of Peyer's plaques. They are mainly found in the lamina propria mucosae, but can sometimes extend into the submucosa. The follicles bulge into the lumen of the appendix. The epithelium at this point is called follicle-associated epithelium (FAE) or dome epithelium. The crypts are usually absent here.

As an appendage of the caecum, the appendix is usually located intraperitoneally, i.e. it is surrounded by a serosa and has a mesoappendix.

The appendix belongs to the so-called GALT. It is a lymphatic organ that has an immunoregulatory function. In addition, it probably serves as a microbiome reservoir that enables rapid recolonisation of the colon with the physiological bacterial flora familiar to the immune system after diarrhoea.

Inflammation of the appendix is known as appendicitis. Neoplasia of the appendix accounts for approx. 0.5 % of all gastrointestinal neoplasia.

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