Biomedical Engineering Reference
In-Depth Information
The crystal lattice of collagen fibers are embedded in an amorphous matrix. The amorphous
matrix is composed mainly by glycosaminoglycans as proteoglycans (sulphated
glycosaminoglycans bound to proteins). In this matrix, in addition to the fibers, tissue cells and
interstitial fluid (water or electrolytes) are embedded. The glycosaminoglycans are negatively
charged polysaccharides of varying degrees of complexity. The glycosaminoglycan polymers
consist of repeating disaccharide units, usually consisting of a hexosamine and an uronic acid
(Yeung et al., 2001). The charged negatively units contribute to the elasticity and hydration of
the tissues (Mavrilas et al., 2005), but may attract counter-ions, which could intervene in the
processes of calcification of bioprostheses. The repetitive disaccharide unit of
glycosaminoglycans mainly presents in native bovine perichardium is shown in figure 2.
Fig. 2. Repetitive disaccharide units of common glycosaminoglycans in bovine perichardial
tissue
The different soft tissues including cartilage, tendons, ligaments, skin and perichardium have
the capacity of support mechanical load of variable magnitude. Therefore, the properties of the
tissue depend on the number and the arrangement of collagen fibers, which can be parallel or
perpendicular to the surface or randomly distributed in the matrix. The hierarchical nature of
collagen confers to the tissue its structural complexity. The fibrous nature of bovine
perichardial tissue is revealed in figure 3. In perichardial tissue, a multi-laminate structure is
observed with difference in both serosa (Fig. 3b) and rugosa surface (Fig. 3a).
Fig. 3. SEM micrographs for the fibrosa (a) and the serosa surface (b) of native bovine
perichardium
