Capillary glucose (such as in blood glucose monitoring), hemoglobin, pH and lactate Capillary blood sampling is generally performed by creating a small cut using a blood lancet, followed by sampling by capillary action on the cut with a test strip or small pipe. Contrary to a popular misconception, William Harvey did not explicitly predict the existence of capillaries, but he clearly saw the need for some sort of connection between the arterial and venous systems. He wrote, "…the blood doth enter into every member through the arteries, and does return by the veins, and that the veins are the vessels and
Vascular remodelling in the embryo to the venous network, effectively changing their identity. This is thought to be due to the high luminal pressure in the arterial lines, which prevents reattachment of the branches back onto arterial vessels. This also prevents the formation of shunts between the two components of the network. Researchers have verified this identity-switching phenomenon by successfully grafting sections of quail endothelial tubing which had previously expressed arterial markers onto chick veins (or vice versa), showcasing the plasticity of the system. Reversing flow patterns in arteries and/or veins can also have the same effect, although it is unclear whether this is due