In healthy myofibers (fully differentiated muscle cells) nuclei are positioned around the cell periphery.

What are Myofibrils made of?

Myofibrils are composed of overlapping thick and thin myofilaments organized into distinct, repeating units called sarcomeres. Z-discs (also called Z-lines; Z in Figures 5.1, 5.2), comprised largely of α-actinin, form the boundaries of sarcomeres and provide an attachment site for thin filaments.

Do muscle cells have a nuclei?

A skeletal muscle cell is long and threadlike with many nuclei and is called a muscle fiber. Muscle cells (including myocytes and muscle fibers) develop from embryonic precursor cells called myoblasts. ... Smooth muscle cells have a single nucleus.