Dermal bone: Difference between revisions

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{{Unreferenced|date=December 2009}}
A '''dermal bone''' or '''membrane bone''' is a bony structure derived from [[intramembranous ossification]] forming components of the [[vertebrate]] [[skeleton]] including much of the [[skull]], [[jaw]]s, [[gill]] covers, shoulder girdle and [[fin]] spines rays ([[lepidotrichia]]), and the [[shell]] (of [[tortoise]]s and [[turtle]]s). In contrast to [[endochondral ossification|endochondral]] bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented<ref name=Bu15>{{cite journal| last1=de Buffrénil |first1=V. | last2=Clarac |first2=F.| last3=Fau |first3=M.| last4=Martin | first4=S.| last5=Martin |first5=B.| last6=Pellé |first6=E.|last7=Laurin |first7=M.|year=2015 |title=Differentiation and growth of bone ornamentation in vertebrates: a comparative histological study among the Crocodylomorpha |journal=Journal of Morphology |volume=276 |issue=4 |pages=425–445 |URL=http://onlinelibrary.wiley.com/doi/10.1002/jmor.20351/abstract}}</ref>. Dermal bone is formed within the [[dermis]] and grows by accretion only – the outer portion of the bone is deposited by [[osteoblast]]s.
 
The function of some dermal bone is conserved throughout vertebrates, although there is variation in shape and in the number of bones in the [[skull roof]] and postcranial structures. In [[bony fish]], dermal bone is found in the fin [[Ray (fish fin anatomy)|rays]] and scales. Special examples of dermal bones include the [[clavicle]], [[patella]], and ''[[os cordis]]''.