Myofilament

Myofilament
Myofilament
Details
Identifiers
Latin	myofilamentum
Code	TH H2.00.05.0.00006
Anatomical terminology []

Myofilaments are the filaments of myofibrils, constructed from proteins, principally myosin or actin. Types of muscle are striated muscle (such as skeletal muscle and cardiac muscle), obliquely striated muscle (found in some invertebrates), and smooth muscle. Various arrangements of myofilaments create different muscles. Striated muscle has transverse bands of filaments. In obliquely striated muscle, the filaments are staggered. Smooth muscle has irregular arrangements of filaments.

There are three different types of myofilaments: thick, thin, and elastic filaments.

The protein complex composed of actin and myosin, contractile proteins, is sometimes referred to as "actomyosin". In striated muscle, such as skeletal and cardiac muscle, the actin and myosin filaments each have a specific and constant length in the order of a few micrometers, far less than the length of the elongated muscle cell (a few millimeters in the case of human skeletal muscle cells). The filaments are organized into repeated subunits along the length of the myofibril. These subunits are called sarcomeres.

The contractile nature of this protein complex is based on the structure of the thick and thin filaments. The thick filament, myosin, has a double-headed structure, with the heads positioned at opposite ends of the molecule. During muscle contraction, the heads of the myosin filaments attach to oppositely oriented thin filaments, actin, and pull them past one another. The action of myosin attachment and actin movement results in sarcomere shortening. Muscle contraction consists of the simultaneous shortening of multiple sarcomeres,.

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