Salivary Gland Structure
There are three pairs of salivary glands. The submandibular glands produce 70% of the daily secretion of saliva; the parotids, 25% and the smaller sublinguals only 5% (see top figure). These glands secrete 1 to 2 liters of saliva per day (pH 6 to 7) at a rate of 0.1 ml/min at rest to 4 ml/min during a period of active stimulation. The submaxillary glands contain mucous and serous cells, the sublinguals, contain mostly mucous cells, and the parotid glands have only serous cells. Duct cells line the intercalated and salivary ducts and modify the saliva to be secreted (see bottom figure). Therefore, the composition of saliva depends on the secretions of these pairs of glands.