Duration: 03:36 | Drinking calcium-rich milk strengthens your bones -- but it's not the only thing you can do for a strong and healthy skeleton. Dr. Jen Gunter digs deep into the three layers of bone to explain why they weaken as we age and shares what you can do to maintain a healthy frame for years to come. Want to hear more from Dr. Gunter? Check out her podcast Body Stuff, from the TED Audio Collective.