The midline that's the body is called

The body's mid-line is an imaginary line down the centre of the body that divides the body into left and right. Crossing the body's mid-line is the ability to reach across the middle of the body with the arms and legs.

i think its control and coordinate because im pretty sure thats what tissue does and the joints are what control movement and then your skeletal/ bones provides portection. hope that .