A model is concerned about a new scar on her abdomen. She tells her surgeon that there is practically no scar from the appendix operation done when she was 16, but this new gallbladder scar is "gross." Her appendectomy scar is small, obliquely located on the inferior abdominal surface, and very indistinct. By contrast, the gallbladder scar is large, lumpy, and runs at right angles to the central axis of the body trunk. Can you explain why the scars are so different?