A dermal bone (membrane bone)- bony structures derived from intramembranous ossification that form components of the vertebrate skeleton including the skull, jaws, gills, fins and exoskeleton. In contrast to endochondral bone, dermal bone does not form from cartilage first and then calcify. Dermal bone is formed within the dermis and it grows by accretion only; that is, the outer portion of the bone is deposited by osteocytes.
The function of dermal bone is conserved throughout vertebrates, varying in shape and numbers of bones in the skull roof and postcranial structures. In bony fish, dermal bone is found throughout the body in the fin rays and scales. Special examples of dermal bones include the clavicle, patella, and os cordis.
Famous quotes containing the word bone:
“Sang a bone upon the shore;
“A child found all a child can lack,
Whether of pleasure or of rest,
Upon the abundance of my breast”:
A bone wave-whitened and dried in the wind.
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—William Butler Yeats (1865–1939)