Changes

==='''Organisation of collagen in bone and fibrocartilage'''===

==='''Organisation of collagen in bone and fibrocartilage'''===

   

   

In both bone and fibrocartilage, collagen fibrils are embedded in a matrix.  For bone, the matrix is made of mineral crystals and for cartilage the matrix is mucopolysaccaride. Bone and fibrocartilage are therefore both heterogeneous.  Each is a composite material consisting of several different components.  

In both bone and fibrocartilage, collagen fibrils are embedded in a matrix.  For bone, the matrix is made of mineral crystals and for cartilage the matrix is mucopolysaccaride. Bone and fibrocartilage are therefore both heterogeneous.  Each is a composite material consisting of several different components.  

In bone, collagen forms one third of the weight and one half of the volume of the tissue.  The arrangement of the collagen determines the quality of the bone.  In the most structured bone, the collagen fibres are arranged parallel to one another in sheets, or lamellae, 5µm thick (Fig. 2.12).  The alignment of the collagen alternates between the lamellae.  In some bones, the lamellae form concentric rings around blood vessels.  Each set of such rings is called an osteone.  Not all bone is, however, lamellar bone; such highly organised bone is only common in larger reptiles and mammals.  The predominant component of bone, by weight, is the organic part.  Crystals of hydroxyapatite that lie between the collagen fibrils within each lamella form this.  The resulting mineralised tissue is one twentieth as elastic as pure collagen in tension.

In bone, collagen forms one third of the weight and one half of the volume of the tissue.  The arrangement of the collagen determines the quality of the bone.  In the most structured bone, the collagen fibres are arranged parallel to one another in sheets, or lamellae, 5µm thick (Fig. 2.12).  The alignment of the collagen alternates between the lamellae.  In some bones, the lamellae form concentric rings around blood vessels.  Each set of such rings is called an osteone.  Not all bone is, however, lamellar bone; such highly organised bone is only common in larger reptiles and mammals.  The predominant component of bone, by weight, is the organic part.  Crystals of hydroxyapatite that lie between the collagen fibrils within each lamella form this.  The resulting mineralised tissue is one twentieth as elastic as pure collagen in tension.

Fibrocartilage contains collagen in a less organised pattern than lamellar bone.  The more elastic type of cartilage contains elastin also.  The matrix of cartilage is a polymer made up of proteins and polysaccharides in hydrated complexes, known as mucopolysaccharide.

Fibrocartilage contains collagen in a less organised pattern than lamellar bone.  The more elastic type of cartilage contains elastin also.  The matrix of cartilage is a polymer made up of proteins and polysaccharides in hydrated complexes, known as mucopolysaccharide.

:::::'''Fig. 2.12 Bone structure'''

:::::'''Fig. 2.12 Bone structure'''