Elastic fibers (or yellow fibers) are bundles of proteins (elastin) found in extracellular matrix of connective tissue and produced by fibroblasts and smooth muscle cells in arteries.These fibers can stretch up to 1.5 times their length, and snap back to their original length when relaxed.he elastic fiber is formed from the elastic microfibril (consisting of numerous proteins such as microfibrillar-associated glycoproteins, fibrillin, fibullin, and the elastin receptor) and amorphous elastin.
Venous, Arterial, and Capillary Blood Specimens. Venous Blood. Venous blood is deoxygenated blood that flows from tiny capillary blood vessels within the tissues into progressively larger veins to the right side of the heart.Venous blood is the specimen of choice for most routine laboratory tests.apillary Blood. Capillary blood is obtained from capillary beds that consist of the smallest veins (venules) and arteries (arterioles) of the circulatory system. The venules and arterioles join together in capillary beds forming a mixture of venous and arterial blood.
Veins carry oxygen depleted blood back to your heart. Capillaries are very small veins or arteries. They are small enough that the oxygen can diffuse across the capillary wall into the tissue, and the carbon dioxide can diffuse from the tissue back into the blood. Capillaries are the structure where this gas exchange takes place.