Separate plasma by centrifugation. Transfer the serum, plasma or whole blood to a plastic transport tube (see Pediatric Specimen Tubes below). To prevent injury and exposure to potentially infectious material, do not ship frozen serum, plasma, or whole blood received in glass tubes or SST (glass or plastic).
The capillaries are the smallest of the blood vessels and are part of the microcirculation. The capillaries have a width of a single cell in diameter to aid in the fast and easy diffusion of gases, sugars and nutrients to surrounding tissues.fter travelling from the aorta, blood travels through peripheral arteries into smaller arteries called arterioles, and eventually to capillaries. Arterioles help in regulating blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.
All blood vessels are lined with a thin layer of simple squamous epithelium known as the endothelium that keeps blood cells inside of the blood vessels and prevents clots from forming. The endothelium lines the entire circulatory system, all the way to the interior of the heart, where it is called the endocardium. Venules are similar to arterioles as they are small vessels that connect capillaries, but unlike arterioles, venules connect to veins instead of arteries. 2  Venules pick up blood from many capillaries and deposit it into larger veins for transport back to the heart.