Fig. 1

Cross-sections of PASs from in vivo dye experiments. a We consider PASs in two regions: those adjacent to pial arteries and those adjacent to penetrating arteries. b PAS surrounding a murine pial artery, adapted from [8]. c PAS surrounding a human pial artery, adapted from [7]. d PAS surrounding a murine pial artery, adapted from [36]. e PAS surrounding a murine descending artery, adapted from [6]. f PAS surrounding a murine descending artery, adapted from [37]. For each image b–f, the best-fit inner circular and outer elliptical boundaries are plotted (thin and thick curves, respectively). The model PAS cross-section is the space within the ellipse but outside the circle. The dotted line does not represent an anatomical structure but is included to clearly indicate the fit. The parameter values for these fits are given in Table 1. PASs surrounding pial arteries are oblate, not circular; PASs surrounding descending arteries are more nearly circular, but are not concentric with the artery