In mice, muscles (red), tendons (green), and nerves (blue) of the limbs are largely established by ~14.5 after fertilization. In humans, this occurs after ~9 weeks of embryogenesis.
Image: Here the limb of a Scleraxis-GFPmouse embryo is imaged by confocal microscopy (Nikon A1R). Scleraxis is a basic helix-turn-helix transcription factor expressed in tendon cells. Antibodies to myosin (red) and neurofilaments (blue) label muscle and nerves, respectively. 3D rendering by FluoRender.
