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
Pinniped high metabolism. In addition, the blood vessels in their flippers are adapted for countercurrent exchange. Veins containing cool blood from the body extremities surround arteries, which contain warm blood received from the core of the body. Heat from the arterial blood is transferred to the blood vessels, which then recirculate blood back to the core. The same adaptations that conserve heat while in water tend to inhibit heat loss when out of water. To counteract overheating, many species cool off by flipping sand onto their backs, adding a layer of cool, damp sand that enhances heat loss. The northern fur