Simulated PO2 profiles in the cross section of a selected trabecula (same specimen as in Figs. 3 and 4). The silver-colored regions (including the boundary) indicate collagen. The region outside the cross section represents the respective ventricle. In a and d, its color is red, indicating a PO2 of 100 mm Hg. In b and e, its color is azure, indicating 40 mm Hg, the PO2 of RV blood at rest. In c and f, the color blue indicates extremely low PO2 (20 mm Hg) of blood in the RV during exhausting exercise. The top row shows the simulated PO2 profiles at the arterial ends of the capillary beds, and the bottom row shows them at the venous ends. Note the extensive penetration of O2 from the ventricle into the avascular annulus of peripheral tissue in each case, but especially in d. The bull's-eyes indicate PO2 minima under each condition.
