SECTION 11. BIOCHEMISTRY OF CONNECTIVE TISSUE

Main subjects:

11.1. Glycosaminoglycans

11.2. Collagens

11.3. Elastin

11.4. Adhesive proteins

Human tissues are not composed of cells only. Part of their volume is occupied by extracellular space filled in by a complex net of macromolecules, that constitute extracellular (intracellular) matrix. The matrix includes different polysaccharides and proteins spontaneously organized to form ordered structures. The tissue in which extracellular matrix occupies a considerably larger volume than cells is referred to as «connective tissue» (Fig. 11.1).

Fig. 11.1. Organization: extracellular matrix-basal membrane-epithelium

The connective tissue contacts with the layer of epithelial cells. The basal lamina (very thin and dense membrane) resides between epithelium and extracellular matrix.

Individual's connective tissue provides:

• active exchange of metabolites and ions between the blood and tissues;

• formation of the structure of organs and tissues in embryogenesis and postnatal period;

• flexibility of rubbing surfaces of joints as it forms their covering cartilage;

• protection against external action regulating the functional activity of phagocytes and immune system cells;

• regeneration and replacement of defects by stimulating functional activity and proliferation of tissue cells.

The share of connective tissue varies in different organs: in bones and skin it is the main component. There are differences in quantitative proportion of various types of macromolecules and way of their organization in extracellular matrix of different organs. This promotes the formation of various forms of matrix which provide functional requirements of a particular tissue. Connective tissue can be mineralized forming the hard stone-like bone or tooth structures; or the transparent substance of eye cornea, or the cord-like structure conferring to tendons great resistance to rupture.