The other day, I was sketching in the studio and I got on the discussion of how to draw shoulders with some fellow students. I attempted to explain how the muscles in a shoulder work because if you understand the basics, you can apply it in many more situations. Granted my explanation lacked most of the scientific words and was probably inaccurate in some parts, I feel like i did a good job helping them gain a basic understand. Personally if they wanted a more in depth explanation I would send them to the video below. It is probably not the best video for this on the planet but it does a much better job explaining it than I ever could. I honestly recommend their tutorials to anyone wanting to learn more about human anatomy (I believe it is a good place to start anyway).