The location of the threadlike structure in the rat abdominal tissue layer revealed by scanning electron microscopy. (a) Cross-section of tissue explant including the skin (s), subcutaneous tissue layer (st), and abdominal wall muscle (am). The explant is isolated from the near area of umbilicus on the abdominal middle line. Note that the threadlike structure (arrowheads) is located between the skin and subcutaneous tissue layer. (b) Magnified view of the threadlike structure (square in (a), arrowheads) on the surface of subcutaneous tissue layer. (c) Magnified view of the threadlike structure (square in (b)) showing a bundle structure of three subducts (arrowheads). Note the rough surface of threadlike structure.