Figure 3.

Schematic of oxygen delivery in muscle tissue through diffusion. Up to four oxygen molecules can be bound by one of the haemoglobin molecules present in the red blood cells (1). The partial pressure of oxygen is very high in the blood vessels, but low in the surrounding tissue. Therefore, the oxygen is released by the haemoglobin and diffuses along the gradient towards the surrounding tissue. It permeates the capillary wall (4), which for vessels, consists only of endothelium and its basement membrane. The freed oxygen travels towards the mitochondria in the muscle tissue, by which it will be consumed for adenosine triphosphate generation (2). In muscle tissue, the protein myoglobin is also present, which stores up to one oxygen molecule and releases this if the oxygen demand is very high (3). Schematic is not to scale. Source code for mitochondria from [21].