Previous anatomical studies have failed to resolve the question relating to whether or not collagen fibers, like elastic fibers, are attached to smooth muscle cells in the arterial wall. The current ultrastructural study demonstrates the insertion of collagen fibers to the sacrolemmal dark areas in the smooth muscle cells of the carotid arterial system of the giraffe. It is concluded, therefore, that this morphological linage between collagen and smooth muscle cells may facilitate transmission of the force of contraction between the cells and to the surrounding connective tissue framework since the myofilaments appear to be spatially placed in series with the extracellular collagen fibers at the sarcolemmal dark areas.
