MICROANATOMY

Detailed explanation-1: -The Sarcomere. A sarcomere is defined as the region of a myofibril contained between two cytoskeletal structures called Z-discs (also called Z-lines or Z-bands), and the striated appearance of skeletal muscle fibers is due to the arrangement of the thick and thin myofilaments within each sarcomere (Figure 10.2.

Detailed explanation-2: -Within each muscle fiber are myofibrils-long cylindrical structures that lie parallel to the muscle fiber. Myofibrils run the entire length of the muscle fiber, and because they are only approximately 1.2 µm in diameter, hundreds to thousands can be found inside one muscle fiber.

Detailed explanation-3: -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. Thus the length of the thick filament determines the length of the A band.

Detailed explanation-4: -Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium.

Detailed explanation-5: -Cardiac muscle tissue are present in the walls of the heart, pulmomary veins and superior vena cava. They are cylindrical in shape and are uninucleated (having single nucleus). They have branched fibres. They have faint light and dark bands present which alternate with each other.