Which type of muscle is found in the walls of blood vessels and the digestive system?

Smooth muscle is the type of muscle found in the walls of blood vessels and the digestive system. It is characterized by its non-striated appearance and is under involuntary control, meaning it operates without conscious thought. This type of muscle is designed to facilitate processes such as peristalsis in the digestive tract, which helps to move food through the system, as well as regulating blood flow and pressure by contracting and relaxing in the blood vessels.

In contrast, skeletal muscle is striated and attached to bones, allowing for voluntary movements. Cardiac muscle, also striated but involuntary, is specific to the heart and is responsible for pumping blood throughout the body. The term "voluntary" refers to muscles that are consciously controlled, which would not include smooth muscle, as it functions automatically. Thus, smooth muscle plays a crucial role in the functioning of internal organs by contributing to movements that are essential for survival and homeostasis.