Dermal bone: Difference between revisions

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(Tried to rewrite in proper English.)
{{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 the [[skull]], [[jaw]]s, [[gill]]s, [[fin]]s and [[exoskeleton]] (of [[tortoise]]s and [[turtle]]s). In contrast to [[endochondral ossification|endochondral]] bone, dermal bone does not form from cartilage that then calcifies. Dermal bone is formed within the [[dermis]] and grows by accretion only – the outer portion of the bone is deposited by [[osteocyteosteoblast]]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]]''.
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