The sarcomers are made up fro two types of overlapping
structures, thick myosin filaments lying parallel to an
another, and thin filaments made up of F-actin and also
arranged in parallel. The dark outer regions of the A band
contain both thick and thin filaments, while in the
control H zone there are only myosin filaments. The 2
lines correspond to sites where the thin filaments are
anchored to a so called Z disc.