MICROANATOMY

Detailed explanation-1: -The light bands are called I bands and contain only thin filaments. The dark bands are called A bands and contain thick and thin filaments, with the thick filaments running the entire length of the A band.

Detailed explanation-2: -The characteristic ‘striations’ of skeletal and cardiac muscle are readily observable by light microscopy as alternating light and dark bands on longitudinal sections. The light band, (known as the I-band) is made up of thin filaments, whereas the dark band (known as the A-band) is made up of thick filaments.

Detailed explanation-3: -I bands are composed of thin actin filaments and proteins that bind actin and they are bisected by the Z line. The thin filaments extend in each direction from the Z-disk, where they do not overlap the thick filaments, they create the light I band.

Detailed explanation-4: -Each I band has a dense line running vertically through the middle called a Z disc or Z line. The Z discs mark the border of units called sarcomeres, which are the functional units of skeletal muscle.