Give information regarding characteristics of muscles and its types.

(N/A) $-\quad$ Muscle is a specialised tissue of mesodermal origin.
$\Rightarrow$ It contributes to $40-50 \%$ of the body weight of a human adult.
- Muscles possess special properties like excitability,contractility,extensibility,and elasticity.
- Muscles are classified based on different criteria,such as location,appearance,and nature of regulation.
- Based on their location,there are three types of muscles: $(i)$ Skeletal muscles,$(ii)$ Visceral muscles,and $(iii)$ Cardiac muscles.
$(i)$ Skeletal muscles: These are closely associated with the skeletal components of the body (e.g.,limbs,trunk).
- Under the microscope,they show dark and light stripes,hence they are called striated muscles.
- They are under the control of the voluntary nervous system,hence they are known as voluntary muscles.
- These muscles are involved in locomotory actions and changes in body posture.
$(ii)$ Visceral muscles (Non-striated): These are located in the inner walls of hollow visceral organs of the body,such as the alimentary canal,reproductive tract,and trachea.
- They do not show striations and appear smooth,hence they are called smooth muscles (non-striated muscles).
- Their activities are not under voluntary control,hence they are known as involuntary muscles.
- They assist in functions like the transportation of food through the digestive tract and gametes through the genital tract.
$(iii)$ Cardiac muscles: These are the muscles of the heart. Many cardiac muscle cells assemble in a branching pattern. Cardiac muscles are short,cylindrical,and connected to each other by branching processes.
- These muscles are innervated by the autonomic nervous system,so they are involuntary in nature.
- Contraction of cardiac muscles is rhythmic,rapid,and continuous (they do not get fatigued). They are connected by intercalated discs and receive a rich blood supply.