Page 536 - Atlas of Histology with Functional Correlations

breakdown of starch into smaller carbohydrates during the time that food is

in the oral cavity. Once the bolus enters the stomach, it is acidified by gastric
juices. This action decreases amylase activity and carbohydrate digestion.

Saliva also controls bacterial flora in the oral cavity and protects it
against oral pathogens. The bacterial enzyme, lysozyme, secreted by serous
cells hydrolyzes cell walls of bacteria and inhibits their growth in the oral

cavity. In addition, saliva contains salivary antibodies primarily
immunoglobulin A, produced by the plasma cells located in the connective
tissue of salivary glands. Salivary acinar cells secrete a protein component
that binds to and transports the immunoglobulins from plasma cells in the

connective tissue into saliva. The antibodies then form complexes with
antigens and assist in immunologic defense against oral bacteria.

As saliva flows through the duct system of salivary glands, the salivary
ducts modify its ionic content by selective transport, resorption, or secretions
of ions. The striated ducts actively reabsorb sodium and chloride ions from

saliva, whereas potassium and bicarbonate ions, the buffering ions produced
in the striated ducts, are added to the salivary secretions, forming a hypotonic
saliva. The numerous infoldings of the basal cell membrane or striations in

the striated ducts contain elongated mitochondria that provide the necessary
energy for fluid and electrolyte transports across the cell membranes.

The striated ducts of each lobule drain into interlobular or excretory
ducts that eventually form the main duct for each gland, which ultimately
empties its contents into the oral cavity.

Summary

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