Explain the structure of three types of muscle fibres. Also write the locations where they are found in the body.

The following are the three types of muscle cells:

(i) Smooth muscle fibres :They are also known as Unstriped muscles. They are involuntary in nature. This type of muscular tissue consists of spindle-shaped, long fibre-like cell with a nucleus at the centre. The ends are undivided. This type of muscles is present in alimentary canal, muscular coat of blood vessels etc.

(ii) Striated muscles. (Also known as striped or voluntary muscles because of their function being in our control or will). This type of muscular tissue cells are very long fibres, enclosed in a membrane known as sarcolemma. The cells (fibre) are multi-nucleated. Each fibre has several longitudinal myofibrils embedded in cytoplasm. On these myofibrils are present characteristic light and dark bands which give it a striated appearance. These muscles are attached to the skeleton; so are also called skeletal muscles,

(iii) Cardiac muscles. These muscles are found in heart. They are not under the control of the will. They contract rhythmically and involuntarily throughout life without the sign of fatigue.

Structurally they show the characters of both unstriated and striated muscles. They are made up of branched fibres. These fibres are multinucleated and show alternate light and dark bands (striation).

Muscular tissue —A. Unstriped. B. Striped. C. Cardiac.