Figure 2: (a), (b), and (c) are stereo-microscopy images of a pig femoral head for three different age groups, unstained sections, which show the development of mammillary processes with age. (a), (b), and (c) are thin sections of the middle of the femoral head (cut along a plane in which the caput-collum-diaphysis angle is measured) for a 20-, 35- and 480-day-old pig, respectively. The different contrast between right and left sides of (c) is due to varying slice thicknesses. (d), (e), and (f) are sections stained with Masson’s Trichrome adjacent to those of (a), (b), and (c), respectively. AC = Articular cartilage, GP = Growth Plate cartilage, EP = Epiphysis, MP = Metaphysis. Black arrows indicate the undulation of the tubercle in the femoral head; red arrows denote the metaphyseal mammillary process and blue arrows point to the epiphyseal mammillary process. Arrowhead marks secondary mammillary processes. The scale bar is 2 mm.