Here's why:
* Muscles contract and relax: This is the fundamental mechanism of movement. Muscles pull on bones, causing them to move at joints.
* Skeletal system works with muscles: The skeletal system provides the framework and structure that muscles attach to.
* Nervous system controls muscles: The nervous system sends signals to muscles, telling them when and how to contract.
While the circulatory system (blood flow) and respiratory system (oxygen supply) are essential for providing energy to muscles, they are not directly responsible for movement.
