Sarcomere. The thick filaments lies parallel to one another and thin filaments are present in orderly array between the thick filaments. In the centre of the I-band, there is a band of a morphous material called Z-line. In the middle of the A-band a comparatively less darkz one called H-zone or band is present. The area between the two Z-lines is called sarcomere. M line is present, in the middle of H-zone.