Hank tells us about the team of deadly ninja assassins that is tasked with protecting our bodies from all the bad guys that want to kill us - also known as our immune system. Crash Course Biology is now available on DVD! http://dft.ba/-8bCC Like CrashCourse - http://www.facebook.com/YouTubeCrashCourse Follow CrashCourse - http://www.twitter.com/TheCrashCourse Table of Contents 1) Innate Immune System 1:45 a) Mucous Membranes 2:54 b) Inflammatory Response 3:44 c) Leukocytes 4:45 2) Open Le