Overview
Muscle tissue is specialised for contraction and is of three types: skeletal, cardiac and smooth. This topic covers the general properties of muscle cells and the structure, contraction and clinical features of each type, with myoepithelial cells and pericytes as related contractile cells.
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.