In Masson Trichrome, which reagent serves as the post-mordant to enhance staining?

Study for the CAMLPR Histology Practice Test. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

In Masson trichrome, the post-mordant step is used to boost the differential staining and lock in the colors for clear contrast between structures. Bouin's solution acts as this post-mordant—the picric acid in Bouin’s partially fixes the tissue and, with the acetic and formaldhyde components, conditions it so that the subsequent blue (or green) collagen stain binds more intensely. This yields a strong, crisp distinction where collagen appears with the chosen blue/green color while muscle and cytoplasm stain differently, giving the characteristic Masson distinction. The other reagents have different roles: the phosphomolybdic–phosphotungstic acid step acts as the mordant preparing for the collagen dye, the iron hematoxylin stains nuclei, and the light green (or alternative counterstain) provides the contrasting color for non-collagen elements.