You have to talk about how the muscular system works with other systems?
The muscular system requires nervous stimulation from the brain and nerves to create the electrical impulses that move muscles.
The muscles rely on hormones from the endocrine system (like testosterone) to change size (why boys have bigger muscles than girls- boys have more testosterone)
Muscles require support from bones to support themselves and allow you to move in lots of different directions (otherwise you'd be a big worm)
The heart muscle drives the blood in the circulatory system
The diaphragm muscle moves your lungs and allows for the respiratory system to exchange oxygen.
The tongue, esophagus, stomach and intestines are all muscles that allow the digestive system to pass food along the absorptive surfaces.
