Multicellular exocrine glands are glands with multiple cells that are formed by invagination from an epithelial sheet. Unlike endocrine glands, multicellular glands do not lose the duct connecting them to the free surface of the epithelial sheet.
Multicellular exocrine glands may be classified based on three factors: the structures of their duct systems, the structures of their secretory parts and the behavior of their secretory parts. The duct systems may be considered simple or compound. The secretory parts may be classified as coiled tubular, alveolar, tubular-alveolar and branched. The secretory behavior may categorize the glands as merecrine, holocrine or apocrine.