Salivary secretion: "A unidirectional movement of fluid, electrolytes and macromolecules into saliva in response to appropriate stimulation".
The key to understanding the mechanism of salivary secretion is in identifying the individual components of the secretory process and then in visualising how these components fit together.
The problem is that there are a lot of components and more than one way of assembling them.
These pages attempt to assemble the components of secretion into a functional whole.
The key words in the definition of secretion are stimulation, fluid, electrolytes & macromolecules and unidirectional.
The only way to achieve a "Unidirectional" movement of fluid, electrolytes and macromolecules across a cell is if one end of the cell behaves differently from the other. It has always been obvious that one end of a secretory acinar cell looks different from the other.
What is much less obvious is that the polarity extends to every aspect of cell function, including the control of secretion.
"Stimulation" encompasses the neural mechanisms that integrate the response to salivary stimuli, such as taste, and the processes within each salivary acinar cell that communicate between the nervous system and the secretory machinery.
Communication between nerves and gland is accomplished by neuro- transmitters (1st messengengers) which activate intracellular 2nd messengers. If this sounds vaguely familiar, then look at the notes for the "Signal Transduction" plenary from year 1.
"fluid", "electrolytes" and "macromolecules" describe defining components of saliva. The unique viscoelastic and antibacterial properties of saliva stem largely from its protein component. The electrolyte content adds acid buffering and remineralization capabilities and the fluid vehicle dilutes and clears the oral environment.