Definition Saliva is a fluid secreted by salivary glands. Pure saliva is the secretion of the major and minor salivary glands; saliva also called whole saliva, mixed saliva or oral fluid.

Oral fluid consisted of: 1. Pure secretions of salivary glands (major and minor glands). 2. Gingival exudates. 3. Food debris. 4. Desquamated epithelial cells . 5. Microorganisms. 6. Neutrophil and leukocytes, from gingival crevice or tonsils. 7. Mucus secretion. 9. Acids (from GIT). I0. Co2 (from lung). 11. O2 (from air). 12. Tears (from eye).

COMPOSITION

Saliva is made up of approx. 99% of water. Organic components Protein 200mg/100ml. enzymes,immunoglobulins,mucins,traces of albumin and polypeptides and glycopeptides. -amylase{Ptyalin} 60-120 mg/100 ml in parotid. 25 mg/100ml in submandibular. Immunoglobulins Ig A Ig G Ig M

Anti bacterial substances Lysosyme Lactoferrin Sialoperoxidase Glycoproteins Proline rich glycoprotein seen in parotid saliva. Other compounds Siatherin Sialin Free amino acids Urea Glucose

Inorganic constituents Sodium Potassium Chloride Bicarbonate Calcium Phosphorus Flouride Thiocyanate

Factors affecting the composition of saliva include: Flow rate, Glandular source, Duration of stimulation, Previous stimulation, Nature of stimulation, Plasma composition (diet), Hormones, Pregnancy, Exercise, Genetic effects, Drugs, Various diseases and Age.

Physiology of salivary gland MECHANISM OF SALIVARY SECRETION Basic types of acinar epithelial cells exist: - serous cells, which secrete a watery fluid, essentially devoid of mucus - mucous cells, which produce a very mucus-rich secretion

Formation of the acinar fluid

CLASSIFICATION 1.Based on anatomic location Parotid gland Sub mandibular gland Sub lingual gland Accessory glands (labial, lingual, palatal buccal,glossopalatine and retromolar) 2. Based on size and amount of secretion Major salivary glands Minor salivary glands  

3. Based on type of secretion Serous Mucous Mixed Parotid glands - Purely serous Submandibular-Predominantly serous, Mixed Sublingual - Predominantly mucous , Mixed Labial,Buccal,Lingual{Ant.}- Mucous , Mixed Palatine,Glossopalatine - Purely mucous. Posterior part of the tongue - Purely mucous Von Ebner’s Glands - Purely serous

Salivary production and oral clearance Salivary flow (SF) index is a parameter allowing stimulated and unstimulated saliva flow to classified as normal, low, or very low (hyposalivation). A healthy person’s mean daily saliva production ranges from (1 to 1.5 L). In adults, normal total stimulated SF ranges from 1 to 3 mL/ min, low ranges from 0.7 to 1.0 mL/min, while hyposalivation is characterized by a SF of less than 0.7 mL/min. The normal unstimulated SF ranges from 0.25 to 0.35 mL/min, low ranges from 0.1 to 0.25 mL/min, while hyposalivation characterized by a SF of less than 0.1 mL/ min. However, the values denominated “normal” for stimulated and unstimulated SF exhibit a large biological variation.

( Oral clearance). residual volume

Factors affection salivary flow rate: Important: Degree of hydration, Body position, Exposure to light, Olfaction (smell), Biological rhythms (Circadian rhythms, Cirannual rhythms), Drugs Unimportant Gender, Body weight, Gland size

Xerostomia a Greek word where xero mean dry while stoma mean mouth. Causes of Xerostomia: (pathological conditions); 1. Sjogren syndrome, diabetes mellitus. 2. Therapeutic radiation. 3. Surgical removal of salivary gland. 4. Congenital absence of salivary gland. 5. Stone in the duct. 6. Malformation of salivary gland. 7. Acute viral infection, anxiety, mental stress, depression.

Functions of saliva 1. Digestive function The presence of salivary amylase helps begin the process of digestion of starch breakdown in the oral cavity. Glycoproteins in the saliva helps to facilitate mastication, bind masticated food into a bolus aiding swallowing, and protects the soft muscosal surface from damage by coarse foods. Saliva acts a solvent to dissolve food substances thus allowing taste.

2. Inhibition of Dental Caries immunological function e.g. secretory IgA enzymatic function via presence of perioxidase, lysozyme mechanical function of cleaning the tooth surface maintenance of supersaturation with respect to hydroxyapatite protective remineralization of carious lesion via ionic action e.g. fluoride, calcium

3.Buffer System in the Saliva The salivary bicarbonate/carbonate buffer system responsible for rapid neutralization of acids produced by the metabolism of microbes in the oral cavity.

4.Formation of Dental Pellicle Saliva protects the tooth surface against wear by creating a film of salivary mucins and proline-rich glycoprotein, forming the dental pellicle. The early pellicle proteins, proline-rich proteins (PRP) and statherin, promote remineralization of the enamel by attracting calcium ions. demineralization is retarded by the pellicle proteins in concert with calcium and phosphate ions in saliva and in the plaque fluid.

5.Antibacterial, Anti-microbial, Anti-fungal Function of Salivary Proteins Secretory IgA prevents the adherence of oral microorganisms to the enamel pellicle via agglutination. Perioxidase inhibits acid production and growth of many oral microbes and fungi. Salivary Lysozyme assists in the lysis of bacteria in conjunction with other antibacterial systems.

6. Prevention of Halitosis and Cleansing of the Oral Cavity Increased water in the saliva and salivary flow reduces halitosis by diluting and eliminating organic constituents of saliva producing methyl mercaptan and H2S. Agglutinated bacteria, food debris and oral epithelial cells are loosened by saliva and subsequently swallowed.

Other functions Protective: provides lubrication of soft oral tissues preventing abrasion during mastication, speech etc. Speech facilitation