Image: submandibular salivary gland, stained with hematoxylin and eosin.
Serous acini: serous secretory cells show a pyramidal shape, with a wide basal surface. The cytoplasm contains granules, which are secretory vesicles known as zymogen granules. After hematoxylin and eosin staining, the basal part of the cell is darker due to the high density of rough endoplasmic reticulum, whereas the apical part is more eosinophil.
Mucous acini: mucous secretory cells are more rounded and store their products into large vesicles known as mucin granules. These granules stain poorly with general staining techniques, but they are strongly labeled by specific staining for carbohydrates, such as PAS.
Myoepithelial cells: they are cells that drive the contraction of the acini and proximal excretory ducts to propel the secreted substances toward the exterior.
Excretory ducts: they are tubules that gathered the secreted substances by the acini. The proximal excretory ducts are made up of walls consisting in one-cell thick layer.
Septum: large salivary glands are divided in lobes, separated to one another by layers of connective tissues known as septa.