Saliva is produced in human body in quantity of 1000 to 1500 ml per day. pH of saliva is 6.35 – 6.85. It is composedof 99.5% water and 0.5% of solutes. 0.5% solutes in saliva are divided further as described below: Organic substances Ions: Sodium Calcium o Urea Potassium Magnasium o Uric acid Chloride Hydrogen o Mucin Bicarbonates Iodine o Globulin Phosphates Iron o Serum Albumin o Lysozyme PROTEOME: o Salivary amylase 106 D glycoprotiens to 1000 D peptides DNA RNA What it is made up of? Saliva is made up of water, mucus, proteins, mineral salts and amylase. As we said earlier,the saliva in the mouth is constantly at work. What does it do, working like a workaholic? As it happens, saliva is nature’s own cleaning system for your mouth. We do take efforts to keep our mouths clean, but we cannot do it all the time and saliva is nature’s way of ensuring it remains so for us. It constantly circulates in the mouth and picks up any debrisleft while eating, bacterial cells formed due to food particles have been left in the mouth and the white blood cells that are automatically released by the body to fight bacteria.Major salivary glands: 1) Parotid Gland 2) Sublingual Gland 3) Submandibular Gland The percentage of contribution by the glands during unstimulated SF is as follows: • 20% by the parotid glands • 65%-70% submandibular glands • 7% to 8% sublingual glands • <10% by the minor salivary glands When SF is stimulated, there is an alteration in the percentage of contribution of each gland with the parotids contributing over 50% of the total salivary secretion.
SECRETORY UNIT(SALIVON): The basic unit “salivon” consists of: Acinus -initial secretory process Intercalated duct -initial portion of duct Striated duct -modification of secretory product Myoepithelial cells surround acinus and intercalated duct contraction moves saliva, prevents development of back pressureComposition:There are 4 major components 1) Mucus – serves as a lubricant 2) Amylase – initiates the digestion of starch 3) Lingual Lipase – begins digestion of fat 4) Electrolyte Solution (Na+, Cl-,K+,HCO3-) – moistens food 5) Proteins & Enzymes – Statherins,Proline-Rich Proteins (PRPs),Histatins,Cystatins,Lysozyme,Salivary PeroxidaseEnzymes: -amylase, parotid glands • cleaves -1 ,4-glycosidic bonds • pH optimum of 7 inactivated @ pH 4 but continues to work for sometime in unmixed food in orad portion of stomach Kallikrein (protease, acinar cells) • Catalyzes production of bradykinin from -globulin • Increase local blood flow Water (0.5 L saliva/day)MUCIN:It is responsible for lubrication, protection against dehydration, and maintenance of salivary visco-elasticity. Theyalso selectively modulate the adhesion of microorganisms to the oral tissue surfaces,which contributes to thecontrol of bacterial and fungal colonization. In addition, they protect these tissues against proteolytic attacks bymicroorganisms. Mastication, speech, and deglutition are aided by the lubricant effects of these proteins. o Lack precise folded structure of globular proteins o symmetrical molecules with open, randomly organized structure o Polypeptide backbone (apomucin) with CHO side-chains
o Side-chains may end in negatively charged groups, such as sialic acid and bound sulfate o Hydrophillic, entraining water (resists dehydration) o Unique rheological properties (e.g. high elasticity, adhesiveness, and low solubility) o Two major mucins (MG1 and MG2)AMYLASE: o Calcium metalloenzyme o Hydrolyzes a(1-4) bonds of starches such as amylose and amylopectin o Several salivary isoenzymes o Maltose is the major end-product (20% is glucose) o “Appears” to have digestive function o Present in tears, serum, bronchial, and male and female urogenital secretions o A role in modulating bacterial adherenceSTATHERINS: o Calcium phosphate salts of dental enamel are soluble under typical conditions of pH and ionic strength o Supersaturation of calcium phosphates maintain enamel integrity o Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid o Produced by acinar cells in salivary glands o Also an effective lubricantPROLINE RICH PROTIENS: o Like statherin, PRPs are also highly asymmetrical o Inhibitors of calcium phosphate crystal growth o Inhibition due to first 30 residues of negatively-charged amino-terminal end o Present in the initially formed enamel pellicle and in “mature” pellicles o Pellicle is formed by selective adsorption of hydroxyapatite-reactive salivary proteins, serum proteins and microbial products such as glucans and glucosyl-transferase o Pellicle acts as a diffusion barrier, slowing both attacks by bacterial acids and loss of dissolved calcium and phosphate ionsLINGUAL LIPASE: o Secreted by von Ebner’s glands of tongue o Involved in first phase of fat digestion o Hydrolyzes medium- to long-chain triglycerides o Important in digestion of milk fat in new-born o Unlike other mammalian lipases, it is highly hydrophobic and readily enters fat globulesHISTATINS:o A group of small histidine-rich proteinso Potent inhibitors of Candida albicans growth
ELECTROLYTE SOLUTION: o 2–21 mmol/L sodium (lower than blood plasma) o 10–36 mmol/L potassium (higher than plasma) o 1.2–2.8 mmol/L calcium (similar to plasma) o 0.08–0.5 mmol/L magnesium o 5–40 mmol/L chloride (lower than plasma) o 25 mmol/L bicarbonate (higher than plasma) o 1.4–39 mmol/L phosphate o Iodine (mmol/L usually higher than plasma, but dependent variable according to dietary iodine intake) o pH changes from being slightly acidic (pH 6-7 ,at rest) to basic (pH 8) at ultimate stimulation ↑ ↑ HCO3- in the salivaCYSTATINS: o Are inhibitors of cysteine-proteases o protective against unwanted proteolysis (bacterial proteases, lysed leukocytes) o inhibit proteases in periodontal tissues o effect on calcium phosphate precipitationSALIVERY PROXIDASE SYSTEM: o Sialoperoxidase (SP) Readily adsorbed to various surfaces of mouth • enamel, salivary sediment, bacteria, dental plaque o Myeloperoxidase (MP) From leukocytes entering via gingival crevice 15-20% of total peroxidase in whole salivaLYSOZYME: o Present in numerous organs and most body fluids o Oral LZ is derived from at least four sources major and minor salivary glands, phagocytic cells and gingival crevicular fluid (GCF) o Biological function o Anti-microbial activity by: Inhibition of bacterial adhesion to tooth surfaces Inhibition of glucose uptake and acid production Muramidase activity (lysis of peptidoglycan layer
Composition of perotid saliva:.pH ………….……………….7.4__7.9The values are expressed as milli-equivalents per liter.HCO3 ............................55.1Cl .......................... 81.7Na ......................... 106.0K ......................... 10.1Ca ...........................7.7Saliva composition when dog isnormal , jumping and in wetcondition shaking its hairs toremove water;Dog saliva contains NO ENZYMEBacteria & viruses are present.
Mean composition of 24 hr collection of parotid saliva: Substance Concentration Number of (m-equiv/l.) + S.D.1 Sodium 47—612 Potassium 12—153 Calcium 11—134 Magnesium 3.3—3.45 Chloride 36—606 Bicarbonate 44—527 Phosphate 0.25—0.288 Volume 4.9—6.3 secreted9 pH 7.47—7.49Others are Proteins, DNA, RNA, Immunnoglobulins, metabolites, drugs & theirmetabolites, viruses, bacteria and cellular material…..