Notice that due to the overlap between the thin and thick filaments, the A band also includes a small portion of our thin filaments. So these small black regions here. Now, what about these Z lines? So the z line number one and the z line number two are basically the boundary lines for our sarcomir. So the sarcomir begins on this z line and ends on the z line, while the second sarcommer here begins on the z line and ends on the other z line that is not shown. And it's the z line that basically gives skeletal muscle as well as our cardiac muscle striped or its striped look.