SMALL GRANULES OF SUPERFICIAL EPIDERMIS

Large non-membrane-bound keratohyaline granules and small membrane-bound granules (keratinosomes, membrane-coating granules) abound in the superficial epidermis. Following injection, ferritin is seen in intercellular spaces, within invaginations of the plasma membrane and within the small granules. Phagocytosis of ferritin by small granules supports the concept that they evolve from the cell periphery and move to the cell interior rather than the reverse. Some small granules have a characteristic internal laminated structure, but the majority do not. Most small granules stain positively with periodic acid-silver methenamine for glycogen and mucopolysaccharide. Acid hydrolase activity is diffuse and not localized to small granules within the granular layer, but some granules in the upper spinous layer may stain positively. These variations in structural, histochemical and functional characteristics support the hypothesis that small granules of the superficial epidermis are a heterogenous group of organelles. © 1969 Springer-Verlag.