Write a note on muscle tissue.

(N/A) $ \Rightarrow $ Muscle tissue is associated with the movements of the organs of the body.
$ \Rightarrow $ Each muscle is made of many long, cylindrical fibres arranged in parallel arrays.
$ \Rightarrow $ These fibres are composed of numerous fine fibrils called myofibrils.
$ \Rightarrow $ All muscle fibres contract (shorten) in response to stimulation, then relax and return to their uncontracted state in a coordinated fashion.
$ \Rightarrow $ Their action moves the body to adjust to the changes in the environment and to maintain the positions of the various parts of the body.
$ \Rightarrow $ In general, muscles play an active role in all the movements of the body.
$ \Rightarrow $ Types of muscle tissue:
Muscles are of three types:
$ (i) $ Skeletal muscle tissue
$ (ii) $ Smooth muscle tissue
$ (iii) $ Cardiac muscle tissue
$ (i) $ Skeletal muscle tissue: These are closely attached to skeletal bones. In a typical muscle such as the biceps, striated (striped) skeletal muscle fibres are bundled together in a parallel fashion. $ A $ sheath of tough connective tissue encloses several bundles of muscle fibres.
$ (ii) $ Smooth muscle tissue:
$ \Rightarrow $ Location: The wall of internal organs such as the blood vessels, stomach, and intestine contains this type of muscle tissue.
$ \Rightarrow $ Structure: Each cell is spindle-shaped and has a nucleus in its central broader part. Dark and light bands are not seen in it.
$ \Rightarrow $ They are involuntary in action.
$ (iii) $ Cardiac muscle tissue:
$ \Rightarrow $ Location: This muscle is present only in the wall of the heart.
$ \Rightarrow $ Structure: Cardiac muscle cells are branched and cylindrical. They contain one or two nuclei arranged in the centre.
$ \Rightarrow $ They possess intercalated discs at the ends of the cells, which function as communication junctions. They are involuntary and show rhythmic contraction.