The muscular system comprises all of the muscles in the body, from the larger leg muscles to the smaller muscles inside the eyes. If you are teaching science students about how the muscles function in the body, it can be helpful to create a model demonstrating how a muscle moves inside the body. This model of the muscular system is especially helpful as a teaching tool for visual or kinesthetic learners in the classroom.

Twist two hook screws onto a tennis ball, arranging them on opposite sides.

Drill two holes into one end of each PVC pipe, arranging them on opposite sides.

Twist a hook screw into each drilled hole.

Place the tennis ball in between the two PVC pipes, arranging the pipes so that the hooks are placed away from the ball. Arrange the ball so that the hooks face out on either side.

Hook a bungee cord from the end of one pipe to one of the hooks on the tennis ball.

Hook a second bungee cord onto the same pipe, placing it onto the opposite hook. Hook the other end of the bungee cord to the opposite side of the tennis ball.

Repeat this process with the other PVC pipe.

Inflate a balloon until it is one-third full.

Bend the structure until it is bent at a 90-degree angle.

Place the inflated balloon onto the bent section of the structure.

Tape the ends of the balloon onto the PVC pipes.

Stretch open the structure to demonstrate how the balloon "muscle" stretches out, and bend the structure to demonstrate how the balloon "muscle" contracts.