Saliva
The major salivary glands produce and secrete saliva – parotid, sublingual, and submandibular glands, as well as minor salivary glands located in the tongue, inner lip surface, soft palate area, and cheek mucosa.
The serous cells of salivary glands secrete a protein-rich secretion containing enzymes, while mucous cells secrete mucus. The parotid gland secretes serous saliva, which makes up about 20% of the total saliva volume; the sublingual gland secretes mucous saliva, rich in mucin and making up 5% of the total saliva volume. The submandibular gland secretes the largest amount of mixed saliva.
Saliva is secreted from the major glands when food enters the mouth and stimulates taste receptors, or in response to conditioned reflexes when food is smelled or seen.
The minor salivary glands constantly produce and secrete saliva, which moistens the mouth. Therefore, saliva is a mixture of secretions from all oral glands. 1-2 liters of saliva are secreted per day, with a pH of 5.8-7.8. The secretion is minimal during rest (0.25 ml/min.), but greatly increases during eating or chewing (3-4 ml/min.).
It is a sticky, slightly viscous fluid composed of 98.5-99% water and 1-1.5% organic (proteins, amino acids, ammonia, creatinine, glycoproteins, monosaccharides) and mineral substances dissolved in it.
Salivary glands secrete the enzyme α-amylase, which hydrolyzes carbohydrates. They have bactericidal and bacteriostatic effects. They produce and secrete protective substances: the enzyme lysozyme, which breaks down bacterial cell walls, the iron-containing glycoprotein lactoferrin, which inhibits the growth of pathogenic microorganisms. Immunoglobulins (mostly IgA) secreted in saliva also play a protective role. Saliva also contains the enzyme kallikrein.
Saliva contains certain mineral substances and cations (Na+, K+, Ca2+), anions (J–, Cl–, Br–, HCO3–, H3PO4–, F–).
A significant portion of calcium in saliva is ionized, while another part forms complexes with sulfates or binds to proteins. Calcium acidic carbonates can form dental calculus.
Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė