Figure 1.

Anatomy of cerebral arterioles (top) and capillary (bottom). The innermost layer of arterioles and capillaries is composed of a continuous layer of endothelial cells, linked by tight junctions, and bounded externally by a layer of basement membrane that contains pericytes; arterioles, but not capillaries, travel inside the perivascular Virchow Robin Space (VRS); the outermost layer of the blood brain barrier is composed of astrocyte endfeet, the terminal pads of large astrocyte processes.