Today Hank explains the skeletal system and why astronauts Scott Kelly and Mikhail Kornienko are out in space studying it. He talks about the anatomy of the skeletal system, including the flat, short, and irregular bones, and their individual arrangements of compact and spongy bone. He'll also cover the microanatomy of bones, particularly the osteons and their inner lamella. And finally, he will introduce the process of bone remodeling, which is carried out by crews of osteocytes, osteoblasts, and osteoclasts. Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: https://apple.co/3d4eyZo Download it here for Android Devices: https://bit.ly/2SrDulJ Chapters: Introduction: Astronaut Bones 00:00 Structure of the Skeletal System: Axial & Appendicular Bones 2:33 Bone Shapes: Long, Short, Flat, and Irregular 3:11 Internal Bone Structure 3:47 Osteons and Their Lamellae 5:05 Osteoblasts and Osteoclasts 5:54 Bone Remodeling: Resorption & Apoptosis 7:28 Review 9:28 Credits 10:13 *** Thanks to the following Patrons for their generous monthly contributions that help keep Crash Course free for everyone forever: Mark Brouwer, Jan Schmid, Steve Marshall, Anna-Ester Volozh, Sandra Aft, Brad Wardell, Christian Ludvigsen, Robert Kunz, Jason, A Saslow, Jacob Ash, Jeffrey Thompson, Jessica Simmons, James Craver, Simun Niclasen, SR Foxley, Roger C. Rocha, Nevin, Spoljaric, Eric Knight, Elliot Beter, Jessica Wode, Julie Kaminski, Steven Ness, Hannah!!!!!, Pamela Genise, Mark B. Williams, Becky Kaplan, William Edwards, Rebecca Carlson, Matthew Tryba, Eric Birchfield -- Crash Course is on Patreon! You can support us directly by signing up at http://www.patreon.com/crashcourse Want to find Crash Course elsewhere on the internet? Facebook - http://www.facebook.com/YouTubeCrashCourse Twitter - http://www.twitter.com/TheCrashCourse Instagram - https://www.instagram.com/thecrashcourse/ CC Kids: null