What is the endothelial glycocalyx and its vascular relevance?

• A. A lipid layer storing cholesterol
• B. Glycoprotein-polysaccharide layer lining luminal surface; regulates permeability, mechanotransduction, protects endothelium
• C. The basement membrane
• D. A protein that anchors smooth muscle to endothelium

Answer: (B)

The endothelial glycocalyx is a glycoprotein-polysaccharide layer that coats the luminal surface of blood vessels. This coating acts as a selective barrier, helping regulate what leaks through from the bloodstream into the vessel wall, and it participates in mechanotransduction—sensing shear stress from blood flow and translating it into cellular signals that influence vascular tone and function. It also protects the endothelium by reducing direct contact with circulating cells and contributing to anti-thrombotic properties. In the vascular system, preserving this layer is important for maintaining normal permeability, preventing edema, and modulating inflammation; when it’s damaged or shed, permeability increases and inflammatory processes can be amplified. The basement membrane, by contrast, lies beneath the endothelium and is a separate extracellular matrix mainly composed of collagen IV and laminin, not the surface glycocalyx.