Alternative definition : KEGG: Saliva has manifold functions in maintaining the integrity of the oral tissues,
in protecting teeth from caries, in the tasting and ingestion of food, in speech and
in the tolerance of tenures, for example. Salivary secretion occurs in response to
stimulation by neurotransmitters released from autonomic nerve endings. There are
two secretory pathways: protein exocytosis and fluid secretion. Sympathetic stimulation
leads to the activation of adenylate cyclase and accumulation of intracellular cAMP.
The elevation of cAMP causes the secretion of proteins such as amylase and mucin.
In contrast, parasympathetic stimulation activates phospholipase C and causes the
elevation of intracellular Ca2 , which leads to fluid secretion; that is, water and
ion transport. Ca2 also induces amylase secretion, but the amount is smaller than
that induced by cAMP.;