MICROANATOMY

Detailed explanation-1: -The bundles of myofilaments are called myofibrils. The structure of the sarcomere is traditionally described with dark and light bands visible under the microscope. This banding pattern in sarcomeres is due mainly to the arrangement of thick and thin myofilaments in each unit.

Detailed explanation-2: -The sarcomere is the basic structural and functional unit of the fibril. It is bordered by a Z-band on each end with adjacent I-bands, and there is a central M-line with adjacent H-bands and partially overlapping A-bands. The Z-band (or Z-disk) is a dense fibrous structure made of actin, -actinin, and other proteins.

Detailed explanation-3: -A bands (or anisotropic bands): It is also called the dark band and contains the whole thick filament (myosin). I bands (or isotropic bands): it is called the light band that contains only the thin filament (actin). The thin filament lies between the two thick filaments.