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A coccyx with four vertebrae below the sacrum. The coccyx is formed of three, four or five rudimentary vertebrae.It articulates superiorly with the sacrum.In each of the first three segments may be traced a rudimentary body and articular and transverse processes; the last piece (sometimes the third) is a mere nodule of bone.
The tailbone, at the end of the spine, has lost its original function in assisting balance and mobility, though it still serves some secondary functions, such as being an attachment point for muscles, which explains why it has not degraded further. In rare cases, congenital defect results in a short tail-like structure being present at birth ...
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]
And what's the deal with the tailbone? Humans have many vestigial body parts that may have been useful for our ancestors but are obsolete for us. Useless body parts explained:
In vertebrate animals that evolved to lose their tails (e.g. frogs and hominid primates), the coccyx is the homologous vestigial of the tail. While tails are primarily considered a feature of vertebrates, some invertebrates such as scorpions and springtails , as well as snails and slugs , have tail-like appendages that are also referred to as ...
The coccyx itself is made up of three to five vertebrae, some of which may be fused together. The ventral side of the coccyx is slightly concave whereas the dorsal aspect is slightly convex. Both of these sides have transverse grooves that show where the vestigial coccygeal units had previously fused.
Atavisms have been observed in humans, such as with infants born with vestigial tails (called a "coccygeal process", "coccygeal projection", or "caudal appendage"). [8] Atavism can also be seen in humans who possess large teeth, like those of other primates. [ 9 ]
Vestigial structures and comparisons in embryonic development are largely a contributing factor in anatomical resemblance in concordance with common descent. Since metabolic processes do not leave fossils, research into the evolution of the basic cellular processes is done largely by comparison of existing organisms' physiology and biochemistry .