95
Furthermore, as recently proposed, the highly vascularized sculptured dermal
bones of early tetrapods, “functioned to buffer the respiratory acidosis that would
have resulted from an increased duration on land. These animals likely would
have lacked adequate means for CO 2 elimination, such as the capacity to achieve
the high ventilation rates. This is made possible by costal aspiration, the ability to
lose signifi cant amounts of CO 2 via the skin, or the kidney function necessary to
increase blood HCO 3
− concentrations to levels required to fully compensate for
respiratory acidosis” (see for discussion Janis et al. 2012 ).
Formation of dermal bone in zebrafi sh has been observed after amputation in the
following manner (Quint et al. 2002 ):
“After amputation, epithelial cells migrate from the stump to cover the wound
region, beneath which a blastema containing undifferentiated proliferative
mesenchymal cells forms. Scleroblasts then differentiate within the blastema at the
epithelial mesenchymal interface and begin to secrete the matrix that will form
the new dermal bone”.
Interestingly, specifi c proteoglycans play important role in development of fi sh
dermal bones. Recent studies report about the isolation of a novel lectican gene
from zebrafi sh termed dermacan (Kang et al. 2004 ). Lecticans are representatives of
proteoglycans that are located in matrices of many tissues. Their functions are
related to modulating of the activities of extracellular signalling molecules, to
differentiation of vertebrae, as well as in maintaining the structural integrity of
corresponding tissues. The experimental results suggest that in zebrafi sh dermacan
can play a key role in differentiation and morphogenesis of dermal bones in the
head skeleton, especially for the opercle, the branchiostegal ray, and dentary (Kang
et al. 2004 ).
Perichondral Bone Perichondrum is a thin layer of dense cells growing within
outer surface of any cartilage. The braincases of numerous primitive placoderms
represent well ossifi ed structures with layers of perichondral bone. It is suggested
that perichondrun in the early placoderms, was the only part of the internal skeleton
that could ossify. Interestingly, “the unornamented inner side of the placoderm eye
capsule is actually two paper-thin layers of perichondral bone, enclosing a space
originally fi lled with cartilage” (Young 2008 ).
Perichondrium, taken from the cartilaginous part of a rib, can develop into
normal hyaline cartilage being placed in a joint (Skoog and Johanason 1976 ; Engkvist
and Ohlsen 1979 ). Woo et al. ( 1987 ) demonstrated that this newly-formed tissue had
the hyaline cartilage-like visco-elastic properties. Amiel et al. ( 1988 ), one year after
perichondral grafting, found neocartilage with biochemical and histological features
similar to those of normal articular cartilage.
Endochondral Bone Mineralized tissue known as endochondral bone is unique
because it begins life as cartilage, which serves as template for endochondral bone
development. In paper by Zustin et al. ( 2010 ), see also Blumer et al. ( 2008 ) we can
fi nd that “Endochondral bone formation is a challenging process in that the originally completely avascular cartilaginous anlage becomes highly vascularized and is
eventually replaced by bone and the marrow cavity”. Chondrocytes, osteoblasts and
3.1 Bone
Furthermore, as recently proposed, the highly vascularized sculptured dermal
bones of early tetrapods, “functioned to buffer the respiratory acidosis that would
have resulted from an increased duration on land. These animals likely would
have lacked adequate means for CO 2 elimination, such as the capacity to achieve
the high ventilation rates. This is made possible by costal aspiration, the ability to
lose signifi cant amounts of CO 2 via the skin, or the kidney function necessary to
increase blood HCO 3
− concentrations to levels required to fully compensate for
respiratory acidosis” (see for discussion Janis et al. 2012 ).
Formation of dermal bone in zebrafi sh has been observed after amputation in the
following manner (Quint et al. 2002 ):
“After amputation, epithelial cells migrate from the stump to cover the wound
region, beneath which a blastema containing undifferentiated proliferative
mesenchymal cells forms. Scleroblasts then differentiate within the blastema at the
epithelial mesenchymal interface and begin to secrete the matrix that will form
the new dermal bone”.
Interestingly, specifi c proteoglycans play important role in development of fi sh
dermal bones. Recent studies report about the isolation of a novel lectican gene
from zebrafi sh termed dermacan (Kang et al. 2004 ). Lecticans are representatives of
proteoglycans that are located in matrices of many tissues. Their functions are
related to modulating of the activities of extracellular signalling molecules, to
differentiation of vertebrae, as well as in maintaining the structural integrity of
corresponding tissues. The experimental results suggest that in zebrafi sh dermacan
can play a key role in differentiation and morphogenesis of dermal bones in the
head skeleton, especially for the opercle, the branchiostegal ray, and dentary (Kang
et al. 2004 ).
Perichondral Bone Perichondrum is a thin layer of dense cells growing within
outer surface of any cartilage. The braincases of numerous primitive placoderms
represent well ossifi ed structures with layers of perichondral bone. It is suggested
that perichondrun in the early placoderms, was the only part of the internal skeleton
that could ossify. Interestingly, “the unornamented inner side of the placoderm eye
capsule is actually two paper-thin layers of perichondral bone, enclosing a space
originally fi lled with cartilage” (Young 2008 ).
Perichondrium, taken from the cartilaginous part of a rib, can develop into
normal hyaline cartilage being placed in a joint (Skoog and Johanason 1976 ; Engkvist
and Ohlsen 1979 ). Woo et al. ( 1987 ) demonstrated that this newly-formed tissue had
the hyaline cartilage-like visco-elastic properties. Amiel et al. ( 1988 ), one year after
perichondral grafting, found neocartilage with biochemical and histological features
similar to those of normal articular cartilage.
Endochondral Bone Mineralized tissue known as endochondral bone is unique
because it begins life as cartilage, which serves as template for endochondral bone
development. In paper by Zustin et al. ( 2010 ), see also Blumer et al. ( 2008 ) we can
fi nd that “Endochondral bone formation is a challenging process in that the originally completely avascular cartilaginous anlage becomes highly vascularized and is
eventually replaced by bone and the marrow cavity”. Chondrocytes, osteoblasts and
3.1 Bone