I don't think this is quite correct. The Endothelial cells make up the capillary walls, so they are part of the capillary. To say otherwise would be like saying a water pipe is only the space inside, not the pipe walls themselves... They are more tightly packed and allow less leakage than elsewhere in the body. There are also other cells (Astrocytes) that support these endothelial cells biochemically that do sit outside the endothelial wall.antimatter37 wrote:I think the two approaches are different (I am a non-expert). The blood-brain barrier (BBB) is primarily constructed of Endothelial cells that surround the tiny capillaries throughout the brain, and are thus external to the capillaries themselves.
https://en.wikipedia.org/wiki/Blood%E2% ... in_barrier
