What is the key characteristic of smooth muscle tissue?

The key characteristic of smooth muscle tissue is that it is involuntary and non-striated. This type of muscle is found in the walls of hollow organs such as the intestines, blood vessels, and the bladder, and it plays a crucial role in processes such as digestion and regulation of blood pressure.

Smooth muscle operates without conscious control, meaning it's regulated by the autonomic nervous system, hormones, and other factors. The non-striated nature of smooth muscle arises from its fiber structure; the cells are spindle-shaped and lack the sarcomeres that create the striations found in skeletal and cardiac muscle. This unique structure allows smooth muscle to contract in a more prolonged and sustained manner, which is essential for its functional roles in the body.

Understanding these characteristics is critical for recognizing the different types of muscle tissues in human anatomy and physiology, especially in environments like the clinic or during physical therapy.