Which component is NOT part of the muscular system?

Vacuoles are not part of the muscular system. In biological terms, vacuoles are membrane-bound organelles found primarily in plant and fungal cells. They serve various functions such as storage, waste disposal, and maintaining turgor pressure within the cell, but they have no role in muscle contraction or movement.

In contrast, the muscular system is comprised of three main types of muscle tissue: cardiac muscle, which makes up the heart and is responsible for pumping blood; skeletal muscle, which attaches to bones and facilitates voluntary movement; and smooth muscle, which is found in the walls of hollow organs and is responsible for involuntary movements. Each of these muscle types plays a crucial role in the function of the human body, distinguishing them from structures like vacuoles that are not involved in muscular activities.