Figure 1. Mouse masseter muscle anatomy depicted for each layer of the muscle: superficial (A), intermediate (B), and deep (C). Tendons of origin (tendon a and tendon b) and insertion (tendon c) are shown, along with the motor endplate distribution. Note that each layer has a continuous row of endplates that does not subdivide the muscle into compartments. The locations of the horizontal sections are also shown (1-4).