Which statement correctly identifies the glycocalyx in the capillary wall?

• A. Glycocalyx lines the luminal surface and contributes to permeability.
• B. Glycocalyx is in the tunica media.
• C. Glycocalyx is a deep basement layer in the adventitia.
• D. Glycocalyx is on the outer surface of veins.

Answer: (B)

Glycocalyx is a gel-like coating on the luminal surface of the endothelial cells that line capillaries. This layer faces the blood inside the vessel and acts as a selective barrier, helping regulate what passes through the endothelium and interacting with circulating proteins and cells. It also participates in sensing and responding to shear stress from blood flow. It is not located in the tunica media (the smooth muscle layer), nor is it a deep basement layer in the adventitia, nor is it on the outer surface of veins. The correct idea is that the glycocalyx lines the luminal surface and contributes to permeability.