Red blood cells are the oxygen-delivering parts of the blood. They must pass through arteries, veins, and capillaries. There is just one problem. “RBCs are twice the diameter of a capillary but can actually squeeze through it. How? Structural properties in the RBC’s membrane allow the cell shape to be incredibly deformed and then spring back to normal. Five specialized structural proteins confer this important ability and a genetic defect in any causes diseases due to rupturing of less-flexible RBC membranes. RBCs are themselves living tissues. It would be possible for RBCs to consume much of their oxygen payload with little left to supply other tissues. However, RBCs have enzymes to power their metabolic processes without the use of oxygen–so they consume none of their precious cargo.” There are also organs which need oxygen but would not function properly with RED blood cells (like the eye). These structures have been designed to filter out the oxygen from the RBCs which would otherwise hinder their function. Even down to the tiniest part of our bodies, God’s masterful creation is amazing. We are “fearfully and wonderfully made” as David said.
From: “Made In His Image: Life-Giving Blood” by Randy J. Guliuzza, P.E., M.D.