The Intercellular Matrix
 ground substance: a viscous, clear substance with a
high water content
 composed of proteoglycans which are made of a
protein core with attached glycosaminoglycans  or
GAGs.
Important GAGs are hyaluronic acid,
chondroitin sulfate, heparan sulfate
(produces the anticoagulant heparin),
keratan sulfate (produces keratin).