Partial failure of lamellar body exocytosis is evident in flaky tail (FT) epidermis (A, C). Note lamellar bodies lined up in peripheral cytosol (A, multiple thin arrows); decreased secreted material at stratum granulosum (SG)-stratum corneum (SC) interface (A&C, short, fat arrows); decreased numbers of lamellar bilayers (C): delayed maturation of lamellar bilayers (C); and entombed lamellar body contents within the corneocyte cytosol (C, short, thin arrows). B&D: Normal lamellar body secretion (B, arrows) and extracellular lamellar bilayers in wild-type (WT) epidermis (D, thin arrows) A&B, osmium tetroxide post-fixation; C&D, ruthenium tetroxide post-fixation. Mag bars = A&C, 0.5 µm; B&D, 0.1 µm.