Two components of endothelial biology – endothelial glycocalyx, endothelial activation – have been explored this two-part, in-depth research project. An extensive literature review discusses the endothelial glycocalyx in health and critical illness. A prospective observational clinical research study then measures the concentration of soluble biomarkers of endothelial activation in severely septic dogs. The study found a significant difference in the concentration of biomarkers between the septic dogs and controls, a result consistent with the presence of endothelial activation in dogs with severe sepsis.