Normal histology of porcine common bile duct. 3A: Intact biliary mucosa overlying a thin fibromuscular wall. Adipose tissue comprises the majority of the adventitia. (original magnification 40×, H&E stain) 3B: Only scattered mononuclear cells are present in the biliary mucosa. (original magnification 400×, H&E stain) 3C: Masson trichrome stain highlights normal collagen content (blue staining) (original magnification 40×) 3D: Normal collagen fibers are thin and reticular in nature. (original magnification 400×, Masson trichrome stain).