★ `color{violet}("Muscle")` is a specialised tissue of `color{brown}("mesodermal origin.")`

★ About `color{brown}("40-50 %)` of the body weight of a human adult is `color{violet}("contributed by muscles.")`

★ They have special properties like `color{brown}("excitability, contractility, extensibility")` and `color{brown}("elasticity.")`

★ `color{violet}("Muscles")` have been classified using different criteria, namely location, appearance and `color{violet}("nature of regulation")` of their activities.

★ Based on `color{violet}("their location")`, three types of `color{violet}("muscles")` are identified :

`color{brown}("(i) Skeletal (ii) Visceral and (iii) Cardiac.")`

★ `color{brown}("Skeletal muscles")` are closely associated with the skeletal `color{violet}(" components of the body.")`

★ They have a striped appearance under the `color{violet}("microscope")` and hence are called `color{brown}("striated muscles.")`

★ As their activities are under the voluntary control of the `color{violet}("nervous system")`, they are known as `color{brown}("voluntary muscles")` too.

★ They are primarily involved in `color{violet}("locomotory actions")` and changes of body postures.

★ `color{brown}("Visceral muscles")` are `color{violet}("located")` in the `color{violet}("inner walls")` of `color{violet}("hollow visceral organs")` of the body like the alimentary canal, reproductive tract, etc.

★ They do not `color{violet}("exhibit any striation")` and are `color{violet}("smooth in appearance.")`

★ Hence, they are called `color{brown}("smooth muscles")` `color{brown}("(nonstriated muscle).")`

★ Their activities are not under the `color{violet}("voluntary control")` of the `color{violet}("nervous system")` and are therefore known as `color{brown}("involuntary muscles.")`

★ They assist, for example, in the `color{violet}("transportation of food")` through the digestive tract and gametes through the `color{violet}("genital tract.")`

★ `color{brown}("Cardiac muscles")` are the `color{violet}("muscles of heart.")`

★ Many `color{violet}("cardiac muscle cells")` assemble in a `color{brown}("branching pattern")` to form a `color{violet}("cardiac muscle.")`

★ Based on appearance, `color{violet}("cardiac muscles")` are `color{brown}("striated.")`

★ They are `color{brown}("involuntary")` in nature as the `color{violet}("nervous system")` does not control their activities directly.