Sarcomere units in striated muscle.

<p>Sarcomeres consist of a parallel arrangement of thick filaments of myosin (gray) sliding along thin filaments of actin (green). They are embedded between Z-lines (red), which appear as dark lines under the transmission electron microscope. In healthy muscle, through the dynamic assembly and disassembly, individual sarcomere units maintain an optimal operating length. Adopted with permission from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045661#pone.0045661-Gktepe1" target="_blank">[16]</a>.