references
http://www.livescience.com/40712-immune-system-surprising-facts.html
http://www.livescience.com/immune/study/system.html
me!
http://www.wisegeekhealth.com/what-is-the-connection-between-the-circulatory-system-and-immune-system.htm
http://www.innerbody.com/image/lympov.html
http://sciencenetlinks.com/student-teacher-sheets/integumentary-system/
http://www.webmd.com/a-to-z-guides/components-of-the-immune-system
http://www.livescience.com/immune/study/system.html
me!
http://www.wisegeekhealth.com/what-is-the-connection-between-the-circulatory-system-and-immune-system.htm
http://www.innerbody.com/image/lympov.html
http://sciencenetlinks.com/student-teacher-sheets/integumentary-system/
http://www.webmd.com/a-to-z-guides/components-of-the-immune-system