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In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function.. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
The human appendix averages 9 cm (3.5 in) in length, ranging from 5 to 35 cm (2.0 to 13.8 in). The diameter of the appendix is 6 mm (0.24 in), and more than 6 mm (0.24 in) is considered a thickened or inflamed appendix.
Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
The appendix, long misunderstood as a vestigial organ, is now recognized as a key MALT structure, playing an essential role in B-lymphocyte-mediated immune responses, hosting extrathymically derived T-lymphocytes, regulating pathogens through its lymphatic vessels, and potentially producing early defenses against diseases. [1]
An appendectomy (American English) or appendicectomy (British English) is a surgical operation in which the vermiform appendix (a portion of the intestine) is removed. Appendectomy is normally performed as an urgent or emergency procedure to treat complicated acute appendicitis. [1]
Humans can live without the gallbladder. [10] The largest lymphatic organ is the spleen, which is dark purple and located under the lower ribs, around the left side of the upper abdomen. [11] [12] It filters the red blood cells by extracting old cells. [11] [12] Coming off the side of the cecum (the tiny tail piece) is the appendix. It is a ...
The appendix apparently serves as a "safe house" for the good bacteria, protecting that supply of bacteria from contamination and facilitating a re-start of the system once the contaminating organism has been eliminated.
[1] [2] It descends behind the termination of the ileum and enters the mesoappendix of the vermiform appendix. It runs near the free margin of the mesoappendix and ends in branches which supply the appendix. Micrograph of entry point of appendicular arteries (arrows at level of inner muscular layer), not to be confused with a perforation.