Muscle tissue (overview)
Textus muscularis
Also known as: muscle tissue types, skeletal muscle, cardiac muscle, smooth muscle, striated muscle
Tissue of elongated, excitable cells (fibres) packed with actin and myosin that contract to produce movement; three types — skeletal, cardiac and smooth — differ in structure, control and regenerative capacity.
Overview
All muscle cells are excitable, contractile, extensible and elastic, and generate force by ATP-driven sliding of myosin over actin filaments, triggered by a rise in cytosolic Ca²⁺. Muscle-specific terms: sarcolemma (plasma membrane), sarcoplasm (cytoplasm), sarcoplasmic reticulum (SER).
Skeletal muscle fibres are very long (up to tens of centimetres), cylindrical, multinucleated syncytia with peripheral nuclei, and striated (regular sarcomeres). They are under voluntary control by somatic motor neurons at neuromuscular junctions, and regenerate to a limited extent from satellite cells. Cardiac muscle cells are branched, striated, with 1–2 central nuclei, joined end to end by intercalated discs (desmosomes and adherens-type junctions for mechanical coupling, gap junctions for electrical coupling); contraction is involuntary and intrinsically rhythmic, modulated by the autonomic nervous system; adult cardiomyocytes are essentially permanent cells, so infarcts heal by scarring. Smooth muscle cells are spindle-shaped, non-striated (actin and myosin anchored at dense bodies), with a single central nucleus; they are involuntary, contract slowly and economically, are often coupled by gap junctions (single-unit) and can divide (hyperplasia, e.g. uterus in pregnancy).
Muscle tissue is detailed in the Muscular system.
Parts & subdivisions
- Striated, voluntary, multinucleated fibres.
- Striated, involuntary, branched, intercalated discs.
- Non-striated, involuntary, spindle-shaped.
- The multinucleate muscle cell.
- Contractile unit between Z-discs.
Anatomy
- Development
Mostly from mesoderm: skeletal muscle from paraxial mesoderm (somites — myotomes), cardiac muscle from splanchnic lateral-plate mesoderm, smooth muscle from splanchnic mesoderm and local mesenchyme. Exceptions of ectodermal origin: the sphincter and dilator pupillae muscles and myoepithelial cells.
Function
- Movement of the skeleton and of substances through hollow organs.
- Posture and joint stability.
- Heat production (shivering thermogenesis).
- Pumping blood (cardiac muscle).
Clinical significance
Regeneration differs by type
Skeletal muscle repairs via satellite cells (impaired in muscular dystrophies); cardiac muscle cannot regenerate meaningfully (myocardial infarction → fibrous scar, compensatory hypertrophy); smooth muscle regenerates by division of surviving cells and pericytes.
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.