Ecm not an inert glue or scaffolding. mechanical: tensile and compressive strength and elasticity. Protection: buffer against ec change and retention of water. organization: control cell behavior by binding growth factors and interactions with surface receptors. matrix of bone and tooth enamel are mineralized to withstand compression. Several liters of liquid ecm in blood plasma. most typical ecm in connective tissue, which are surrounded by specialized ecm, the bl. main ecm components are gags, col, elastin, fn and ln; and proteoglycans. Gag: unbranched repeated disaccharides, amino sugars, sulfated acetyl-amino sugars and uronic acids. Collagen: three -chains, which form a triple helix. under epithelial cells, coats muscle/fat cells; form glomerular filter, wraps myelin sheath. Also form barrier to certain cells, but is highway for migration. Fibronectin: cells bind to the ecm via bl or via fibronectin. Fibronectin-null mice cannot make blood vessels: provides "stickiness" to ecm.