HA13 shows an example of the continuity between the secretory acinus (a), the intercalated duct (i), and the striated duct (s). The striated ducts have prominent striations (basal infoldings) in their bases. Note the prominent darkly stained granules in the acinar cells. Myoepithelial cells (arrowheads) are present in the acini and the intercalated duct. Plasma cells (arrow) are also present in the connective tissue between secretory units. Where are the antibodies secreted?