Which type of muscle tissue is involuntary and found in the walls of organs?

Smooth muscle is the correct answer because it is a type of involuntary muscle tissue that lines the walls of internal organs, such as the digestive tract, blood vessels, and the bladder. Unlike skeletal muscle, which is under voluntary control and striated in appearance, smooth muscle lacks striations and operates automatically, facilitating functions like peristalsis in the intestines and regulating blood flow through the constriction and dilation of blood vessels. The involuntary nature of smooth muscle allows it to function without conscious control, making it essential for vital physiological processes that sustain life.

Skeletal muscle, on the other hand, is voluntarily controlled and striated, primarily associated with movement of the skeleton. Cardiac muscle, while also striated, is a specialized involuntary muscle found only in the heart, and it operates autonomously but is distinct from smooth muscle. Striated muscle refers to any muscle with a banded appearance, including skeletal and cardiac muscles, but does not encompass smooth muscle. Thus, smooth muscle is uniquely characterized by its involuntary control and its presence in the walls of various organs, setting it apart from other muscle types.