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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 longest appendix ever removed was 26 cm (10 in) long. [3] The appendix is usually located in the lower right quadrant of the abdomen, near the right hip bone. The base of the appendix is located 2 cm (0.79 in) beneath the ileocecal valve that separates the large intestine from the small
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]
In females, the mesonephros degenerates entirely, though vestigial structures such as Gartner's ducts, the epoophoron, and paroophoron are common. In males, a few of the more caudal tubules will survive and give rise to the efferent ductules of the testis , [ 1 ] the epididymis , vas deferens , seminal vesicle , as well as vestigial structures ...
Vestigial structures are anatomical structures of organisms in a species which are considered to have lost much or all of their original function through evolution. [8] These body parts can be classed as additional to the required functioning of the body. In human anatomy, the vermiform appendix is sometimes classed as a vestigial remnant.
Coming off the side of the cecum (the tiny tail piece) is the appendix. It is a small organ attached to the large intestine in the lower right side of the abdomen. Anatomists and medical professionals have traditionally considered the appendix a vestigial organ. Later research suggests that it may have an immunological function. [13]
If a structure was once called vestigial, but is now known to be functional, then calling it "Functioning Vestigial Structures" violates the definition of vestigial, because by definition, it is not vestigial. It was previously called vestigial, but that was a mistake. It is not correct to call the vermiform appendix vestigial.