A YouTube element has been excluded from this version of the text. You can view it online here: pb.libretexts.org/aapi/?p=286 Contributors and Attributions CC licensed content, Shared previously Provi...A YouTube element has been excluded from this version of the text. You can view it online here: pb.libretexts.org/aapi/?p=286 Contributors and Attributions CC licensed content, Shared previously Provided by: Khan Academy. Located at: https://www.khanacademy.org/science/biology/human-biology/muscles/v/anatomy-of-a-muscle-cell. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike