Figure 433 from Chapter 16 (Cytoplasmic matrix and cytoskeleton) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. Smooth muscle of mouse epididymal duct. This micrograph is a high magnification view of actin filaments in cross section from part of the accompanying image CIL:36064 in this image group. In contrast to striated muscle, actin filaments in smooth muscle occur in irregular groups that represent bundles or tracts of parallel flaments. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.