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| Smooth Muscle |
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| It is also called unstriped or nonstriated or involuntary or visceral muscle. |
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| The smooth muscle always occurs in the form of thin sheets. Each sheet has a large number of muscle fibres that are held together by a transparent connective tissue covering. The individual muscle fibres in the sheet are elongated and spindle shaped. They are broader in the middle and tapering at the ends. Each muscle fibre has a limiting membrane represented by the cell membrane. A sarcolemma is absent. The cell membrane encloses a small amount of specialised cytoplasm called sarcoplasm. The muscle fibres are uninucleate and the nucleus is situated in the broadest region of the fibre. The sarcoplasm contains thin myofibrils. However, the myofibrils do not form cross bands or striations. |
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| fig 5.57 Smooth Muscle |
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| The smooth muscle fibres have a poor blood supply. They are supplied with sensory or afferent nerves from the brain and spinal chord. The contractions are slow, rhythmic and sustained. The smooth muscle does not easily experience fatigue. It is described as involuntary, since its functioning is not under the control of the our will. |
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| The smooth muscle occurs in almost all visceral organs in the body except the heart. It is particularly abundant in the blood vessels, alimentary canal and glands and their ducts. |
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