Check out these links to learn more about Human Body Systems:
Check out the many articles and videos on How the Body Works:http://kidshealth.org/kid/htbw/
Lots of links about body systems found on this page:
http://www.kidinfo.com/health/human_body.html
Circulatory System
http://www.youtube.com/watch?v=LqhvmUEdOYY
Excretory System
http://www.youtube.com/watch?v=KTU4_qlhkMw
Muscular System
http://www.youtube.com/watch?v=2QX8B4ZqqIE
Nervous System
http://www.youtube.com/watch?v=i-NgGKSNiNw
Skeletal System
http://www.youtube.com/watch?v=vya4wpS2fgk
Digestive System
http://www.youtube.com/watch?v=JnzwbipJuAA
Integumentary System
http://www.youtube.com/watch?v=no_XRnoNGfE