Figure 1.

Morphology of the salivary glands in the cockroach Periplaneta americana a: Low-power micrograph of the salivary gland complex. The salivary glands are paired and consist of several lobes of secretory acini. The ducts (arrowheads) of each gland unite to a single efferent salivary duct (long arrows) that then fuses with the opposite duct to form the main salivary duct. Two reservoirs (asterisks) are associated with the secretory tissue. The reservoirs open into reservoir ducts (broad arrows) that accompany the efferent salivary ducts. b: Schematic representation of the structural organization of secretory acini. Each acinus consists of two peripheral cells with long microvilli and several central cells with numerous secretory granules. The apical surface of the central cells is covered by a sheath of flattened fenestrated centroacinar cells and by a thin discontinuous layer of cuticule. The central cells are stimulated only by serotonin, whereas the peripharal cells respond to dopamine and probably also to serotonin. The duct cells have basal and apical infoldings and are only responsive to dopamine. Scale bar = 2 mm

Baumann et al. BMC Physiology 2002 2:9   doi:10.1186/1472-6793-2-9
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