After completing this study unit you will be able to:
- Describe the structure of smooth musculature.
- Identify smooth muscle in histological sections.
- Understand the differences between smooth and striated musculature.
Smooth muscle consists of individual, spindle-shaped, thin muscle cells that, with the exception of the heart, line all hollow organs and vessels and form the contractile part of the organ wall (visceral muscles). In contrast to striated muscle, the actin and myosin filaments of smooth muscle are not arranged in sarcomeres, which is why no striations are seen under the microscope.
Smooth muscle contracts more slowly than striated muscle. However, it can shorten to a greater extent, up to a third of the original length, and it has the ability to remain in a contracted state for a long period time without tiring (muscle tone). Smooth muscle is innervated involuntarily via the autonomic or enteric nervous system. It can also be hormonally controlled, as is the case in the uterus, for example, and influenced by local metabolic products.
Watch the following video to learn more about smooth muscle:
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Review the structure of smooth muscle in further detail below: