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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]
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.
In humans and other vertebrates, the pharyngeal arches are derived from all three germ layers (the primary layers of cells that form during embryonic development). [2] Neural crest cells enter these arches where they contribute to features of the skull and facial skeleton such as bone and cartilage. [2]
Pharyngeal clefts resembling gill slits are transiently present during the embryonic stages of tetrapod development. The presence of pharyngeal arches and clefts in the neck of the developing human embryo famously led Ernst Haeckel to postulate that " ontogeny recapitulates phylogeny "; this hypothesis, while false, contains elements of truth ...
Artificial gills are hypothetical devices to allow a human to be able to take in oxygen from surrounding water. This is speculative technology that has not yet been demonstrated. Natural gills work because most animals with gills are thermoconformers (cold-blooded), so they need much less oxygen than a thermoregulator (warm
Bones of the first gill arch became the upper and lower jaw, while those from the second arch became the hyomandibula, ceratohyal and basihyal; this closed two of the seven pairs of gills. The gap between the first and second arches just below the braincase (fused with upper jaw) created a pair of spiracles , which opened in the skin and led to ...
A beetle leg. An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface appendages.