ECM occurs in two basic forms interstitial matrix and basement membrane SitTE-Integrins Fibroblast BASEMENT MEMBRANE Type IV collagen Integrins Laminin Endothelial cells Adhesive Proteoglycan glycoproteins Integrins Fibroblast Proteoglycan INTERSTITIAL MATRIX Type IV collagen Fibrillar collagens Elastin Laminin Proteoglycan and Cross-linked hyaluronan collagen triple helices ProteoglycanECM occurs in two basic forms: interstitial matrix and basement membrane