Overview
Skeletal and smooth muscle both contract by the sliding of actin and myosin filaments, but they differ in structure, in how Ca2+ regulates contraction, and in speed and control. This topic describes each type and ends with a direct comparison.
Muscle tissue: types
Muscle tissue is one of the four basic tissue types in the body, alongside epithelia, connective, and nervous tissues. Its primary function is contractility, enabling movement within organ systems, of blood, and of the body as a whole. Muscle cells, also known as myocytes, are generally elongated and originate from mesodermal cells during embryonic development.
There are three distinct types of muscle tissue based on their structure and function:
- Skeletal (striated) muscle: Characterised by very long, multinucleated cells with cross-striations, allowing quick, forceful, voluntary contractions.
- Cardiac muscle: Also has cross-striations but consists of often branched cells connected by intercalated discs, exhibiting vigorous, rhythmic, involuntary contractions.
- Smooth (visceral) muscle: Composed of fusiform (spindle-shaped) cells that lack striations and undergo slow, involuntary contractions.
Muscle cell cytoplasm is often called sarcoplasm, its smooth endoplasmic reticulum (ER) is the sarcoplasmic reticulum, and the cell membrane is the sarcolemma.