Figure 1.

The scaffold of the endothelial glycocalyx, within the endothelial surface layer, is provided by proteoglycans, syndecan (four subtypes), and glypican-1. Glycosaminoglycans are attached to proteoglycans (e.g., heparan sulfate) or the endothelial surface (hyaluronan). Molecules suspended in the plasma of the endothelial surface layer include proteins such as albumin. These proteins create a protein-poor sub-glycocalyx area that is important for transvascular colloid osmotic pressure balance. For simplicity, structures within the interendothelial cleft are not represented.