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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]
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]
This phenomenon is an automatic-response mechanism that activates even before a human becomes consciously aware that a startling, unexpected or unknown sound has been "heard". [2] That this vestigial response occurs even before becoming consciously aware of a startling noise would explain why the function of ear-perking had evolved in animals.
Humans have many vestigial body parts that may have been useful for our ancestors but are obsolete for us. Useless body parts explained: Show comments. Advertisement. Advertisement.
The formation of goose bumps in humans under stress is considered by some to be a vestigial reflex, [4] though visible piloerection is associated with changes in skin temperature in humans. [5] The reflex of producing goose bumps is known as piloerection or the pilomotor reflex, or, more traditionally, [6] horripilation.
Some humans may have physical remnants of a VNO, but it is vestigial and non-functional. The VNO contains the cell bodies of sensory neurons which have receptors that detect specific non-volatile (liquid) organic compounds which are conveyed to them from the environment.
Vestigial eye in the extant Rhineura floridana and remnant jugal in the extinct Rhineura hatchery (reclassified as Protorhineura hatcherii). [91] [92] Functionless wings in flightless birds such as ostriches, kiwis, cassowaries, and emus. [93] [94] The presence of the plica semilunaris in the human eye—a vestigial remnant of the nictitating ...
What makes a human body structure vestigial is that presently it is useless or almost useless, i.e. having no important function. Greensburger ( talk ) 16:49, 1 September 2011 (UTC) [ reply ] The references you listed do not backup your statements, they mention mainly the appendix, and a few other structures.