8. Ground substance of connective tissue. Structural, chemical and functional characteristics.

In connective tissue the ground substance is an amorphous gel-like substance, produced by the fibroblasts. It surrounds the spaces between the fibres and cells. Ground substance does not have collagen and elastic fibres, but contains the remaining components of the extracellular matrix.

Ground substance is mainly water, it has glycosaminoglycans GAGs, proteoglycans, and glycoproteins. Glycosaminoglycans link together to form proteoglycans which are very good at absorbing water, like a sponge, such that 90% of the extracellular matrix is made up of water. This means that the extracellular matrix is very good at resisting compressive forces and is able to retain high amounts of water. 

Glycosaminoglycans are polysaccharides that retain water. They are negatively charged molecules so they can attract positively-charged sodium and potassium ions which are able to bring in water. 

Proteoglycans and glycoproteins are carbohydrate complexes which regulate the movement of molecules through the extracellular matrix. 

Metachromasia is one property of ground substance in which; change in tissue colour produced by the same stain.

Ground substance is optically homogenous which means they are of the same kind and also hydrophilia, the tendency of the blood and tissues to absorb fluid.