Myofibrils
A myofibril is the single unit of a muscle. They form muscle fibres and contain different regions which some are effected during muscle contraction and relaxation. They are made up of 3 main long proteins; actin, myosin and titin. The previous mentioned proteins are ordered into thin or thick repeating filaments.
Myofibrils are the basis of contraction in skeletal muscle cells. They are cylindrical in shape and are 1-2μm[1] in diameter. The thick and thin filaments overlap each other and are made from different proteins. The thick filaments are made from myosin and the thin are made from actin. Each muscle fibre has many myofirbrils running through them. Skeletal muscle cells are often described as striated this is due to the repeating units of thick and thin filaments[2]. Between each myofibrils there are several mitochondria and sarcoplasms.