92
(HAP) (as inorganic part), nanofi brillar collagen fi bres that support the in vivo
development of mineralised bone, and corresponding vascular tissue that supplies
blood to the living cell components of bone. Since publication by Kölliker ( 1859 ),
the presence of cellular and acellular types in the bone of early vertebrates is well
established. In spite of that the structures of these bone types are similar, the principal
difference between them are the spaces in cellular bone for the osteocytes, which
occur throughout this hard tissue.
One of the structural features of the earliest forms of acellular bone is their
lamination. Corresponding layers were deposited by the dermis. The heterostracans,
which are related to early agnathans, possess acellular bone that is called aspidin
(Tarlo 1963 ). Acellular bone have been also observed in layered bone from more
advanced fi sh like placoderms, where this unique structure is found in the basal
bone layer of the fi sh plates. The second structural feature founded in the most
skeletons of the earliest fi sh is formation of the bone that is produced by the dermis.
Thus, so called dermal bone was localized in the head and trunk, as well as the
scales and biting surfaces inside the mouth. For example the scales and the dermal
bones of dipnoans and crossopterygians were covered with a shiny enameloid layer.
The complex layer known as cosmine (see also Sect. 4.2 in this work), covered an
interconnecting network of fl ask-shaped cavities in the uppermost bone layer.
Numerous specialised bone types have been developed in various species of
early osteichthyans. These bone types differ from each other by the nature and composition of the external layers of the dermal bones, complexity. Their hierarchical
structure was determined by corresponding growth and resorption processes which
were involved in their development.
Both, perichondral bone (a thinly laminated acellular bone) and endochondral
bone , are characteristic examples of such kind of specialized bones. As reviewed by
Obradovic-Wagner and Aspenberg ( 2011 ), these bones possess following features
and functions:
“(a) Perichondral bone is often found surrounding soft tissue that passes through
cartilage, as can be found in placoderms with cartilage braincases where the
nerves and arteries passing through the braincase wall can have perichondral
bone surrounding them. The endogirdles that support the pelvic and pectoral
fi ns is also surrounded by perichondral bone.
(b) Endochondral bone forms around a cartilage precursor. These bones make up
much of the internal skeleton in reptiles and mammals, and forms the arm and
leg bones. This type of bone fi rst evolved as a specialised feature in some
groups of gnathostomes (osteichthyans and acanthodians),” ( http://austhrutime.com/bone.htm ; see also Obradovic-Wagner and Aspenberg 2011 ).
Today, two mechanisms of the bone development are accepted, I mean the
intramembranous bone formation and the endochondral bone formation. Bone
formation is complex, but the three-dimensional positioning of cells and matrices is
straightforward. This process is determined by eventual differentiation of osteoprogenitor cells into either mesenchymal osteoblasts, which synthesize woven bone in
3 Biocomposites and Mineralized Tissues
(HAP) (as inorganic part), nanofi brillar collagen fi bres that support the in vivo
development of mineralised bone, and corresponding vascular tissue that supplies
blood to the living cell components of bone. Since publication by Kölliker ( 1859 ),
the presence of cellular and acellular types in the bone of early vertebrates is well
established. In spite of that the structures of these bone types are similar, the principal
difference between them are the spaces in cellular bone for the osteocytes, which
occur throughout this hard tissue.
One of the structural features of the earliest forms of acellular bone is their
lamination. Corresponding layers were deposited by the dermis. The heterostracans,
which are related to early agnathans, possess acellular bone that is called aspidin
(Tarlo 1963 ). Acellular bone have been also observed in layered bone from more
advanced fi sh like placoderms, where this unique structure is found in the basal
bone layer of the fi sh plates. The second structural feature founded in the most
skeletons of the earliest fi sh is formation of the bone that is produced by the dermis.
Thus, so called dermal bone was localized in the head and trunk, as well as the
scales and biting surfaces inside the mouth. For example the scales and the dermal
bones of dipnoans and crossopterygians were covered with a shiny enameloid layer.
The complex layer known as cosmine (see also Sect. 4.2 in this work), covered an
interconnecting network of fl ask-shaped cavities in the uppermost bone layer.
Numerous specialised bone types have been developed in various species of
early osteichthyans. These bone types differ from each other by the nature and composition of the external layers of the dermal bones, complexity. Their hierarchical
structure was determined by corresponding growth and resorption processes which
were involved in their development.
Both, perichondral bone (a thinly laminated acellular bone) and endochondral
bone , are characteristic examples of such kind of specialized bones. As reviewed by
Obradovic-Wagner and Aspenberg ( 2011 ), these bones possess following features
and functions:
“(a) Perichondral bone is often found surrounding soft tissue that passes through
cartilage, as can be found in placoderms with cartilage braincases where the
nerves and arteries passing through the braincase wall can have perichondral
bone surrounding them. The endogirdles that support the pelvic and pectoral
fi ns is also surrounded by perichondral bone.
(b) Endochondral bone forms around a cartilage precursor. These bones make up
much of the internal skeleton in reptiles and mammals, and forms the arm and
leg bones. This type of bone fi rst evolved as a specialised feature in some
groups of gnathostomes (osteichthyans and acanthodians),” ( http://austhrutime.com/bone.htm ; see also Obradovic-Wagner and Aspenberg 2011 ).
Today, two mechanisms of the bone development are accepted, I mean the
intramembranous bone formation and the endochondral bone formation. Bone
formation is complex, but the three-dimensional positioning of cells and matrices is
straightforward. This process is determined by eventual differentiation of osteoprogenitor cells into either mesenchymal osteoblasts, which synthesize woven bone in
3 Biocomposites and Mineralized Tissues