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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]
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 ...
The nerve of the arch itself runs along the cranial side of the arch and is called post-trematic nerve of the arch. Each arch also receives a branch from the nerve of the succeeding arch called the pre-trematic nerve which runs along the caudal border of the arch. In human embryo, a double innervation is seen only in the first pharyngeal arch.
Thus the zoologist Newman stated in the Scopes Trial: "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities." Some of the vestigial organs or organs containing evolutionary vestigial structures, as listed on the article about him: Adenoids
Gill arches supporting the gills in a pike. Branchial arches or gill arches are a series of paired bony/cartilaginous "loops" behind the throat (pharyngeal cavity) of fish, which support the fish gills. As chordates, all vertebrate embryos develop pharyngeal arches, though the eventual fate of these arches varies between taxa.
They are primarily transmitted by direct human to human contact. But they can be transmitted without touching another human if scabies are on blankets, towels, sheets, and other personal items.
In contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head. The anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow.