Figure 4: Histological sections stained in Sirius red, analyzed under polarized light. Seven days: thin delicate reticularlyarranged type-III collagen fibrils seen in COL (Ia), PHO (Ib), and UAL (Ic). Fourteen days: predominance of type-III collagen fibrils is maintained in COL (IIa), and PHO (IIb), whereas in UAL (IIc) there is predominance of type-I collagen fibers. Twenty-one days: intense deposition of type I collagen fibers seen in COL (IIIa) and PHO (IIIb) whereas in UAL, a mix of wavy and highly interlaced type I and type III collagen fibers is seen.