Mills J W, Prum B E
Am J Anat. 1984 Sep;171(1):91-106. doi: 10.1002/aja.1001710108.
Frog skin contains three distinct types of exocrine glands: granular (poison), mucous, and seromucous. The granular gland forms a syncytial secretory compartment within the acinus, which is surrounded by smooth muscle cells. The mucous and seromucous glands are easily identifiable as distinct glands. The serous and mucous secretory cells are arranged in a semilunar configuration opposite the ductal end and are filled with granules. Within the acinus, located at the ductal pole of the gland, are distinct groups of cells with few or no granules in the cytoplasm. In both the mucous and seromucous gland there is a cell type with abundant mitochondria; the one in the mucous gland is located in the region adjacent to the secretory cells. The duct of these glands is two-layered, with the individual cells appearing morphologically similar to the layers of the skin epithelium as the duct traverses the skin. The duct appears to be patent throughout its length. The morphological heterogeneity and distinct distribution of the cell types within the gland acinus may be indicative of a functional heterogeneity that allows the production of distinctly different types of secretion from the same gland type, depending on the type of stimulus.
颗粒腺（毒腺）、黏液腺和浆液黏液腺。颗粒腺在腺泡内形成一个合胞体分泌区，该分泌区被平滑肌细胞包围。黏液腺和浆液黏液腺很容易被识别为不同的腺体。浆液性和黏液性分泌细胞在导管末端相对处呈半月形排列，并充满颗粒。在腺泡内，位于腺体导管极的是不同的细胞群，其细胞质中颗粒很少或没有颗粒。在黏液腺和浆液黏液腺中都有一种线粒体丰富的细胞类型；黏液腺中的这种细胞位于与分泌细胞相邻的区域。这些腺体的导管是双层的，当导管穿过皮肤时，单个细胞在形态上与皮肤上皮层相似。导管在其全长似乎都是开放的。腺泡内细胞类型的形态异质性和独特分布可能表明存在功能异质性，这使得同一类型的腺体能够根据刺激类型产生明显不同类型的分泌物。
