Saliva
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Saliva

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    Saliva Saliva Presentation Transcript

    • Introduced by: Dr/Abousree El-Lethy بسم الله الرحمن الرحيم
      • Vitamins K and C
      Block: Head & Neck Structure and Function Biochemistry Lecture: Biochemistry of Saliva
      • Saliva is produced in and secreted from acinar cells in salivary glands. Major glands of secretions are parotid submandibular, and sublingual.
      • Daily secretion = 800-1500 mL PH = 6-7
    • Functions of Saliva
      • Moistening food
      • Beginning of digestion
      • Adjust salt appetite
      • Containing factors that inhibit adhesion and destroy bacteria.
    • Outline of multifunctions of salivary secreations Salivary Secretions (3) Anti- Bacterial (4) Buffering (5) Digestion (6) Mineral- ization (7) Lubricat- ion &Visco- elasticity (8) Tissue Coating (1) Anti- Fungal (2) Anti- Viral Carbonic anhydrases, Histatins Amylases, Mucins, Lipase Cystatins, Histatins, Proline- rich proteins, Statherins Mucins, Statherins Amylases, Cystatins, Mucins, Proline-rich proteins, Statherins Histatins Cystatins, Mucins Amylases, Cystatins, Histatins, Mucins, Peroxidases
    • Composition of Saliva
      • 1-Aqueous fluids
      • H2O, α -amylase , lingual lipase , IgA, kallikrein, muramidase (lyses muramic acid of Staphylococcus) & lactoferrin.
      • 2-Electrolytes or inorganics
      • Ca, Ph, F, K, Na & Cl
      • HCO 3 defense enemal against acids (pH5.6) produced by cariogenic bacteria
      • During hypotonic Saliva (low flow rate):
      • High and HCO3 ( Pushes pH of stimulated saliva up to 8 )
      • Low Na and CI−
      • 3-Mucus secretion proteins
      • Mucin
      • Statherins
      • Proline-rich Proteins
      • Anti-microbial proteins
      • Lactoferrin
      • Histatins
      • Lysozyme
      • Cystatins
      • Salivary peroxidase
      • Secretory Immunoglobulins
      • 1) α -amylase, parotid glands
      • It cleaves α -1 ,4-glycosidic bonds of starches such as amylose and amylopectin
      • Maltose is the major end-product (20% is glucose)
      • Optimum pH is 7 and inactivated at pH 4 but continues to work for sometime in unmixed food in oral portion of stomach
      • 2) Lingual lipase ( hydrophobic )
      • It is secreted by von Ebner’s glands of tongue and hydrolyzes lipids
      • It continues working into duodenum
      Enzymes
      • (1) Mucins
      • Asymmetrical molecules of globular proteins with polypeptide backbone (apomucin) and side-chain of negatively charged groups (e.g. sialic acid and bound sulfate).
      • Hydrophillic (resists dehydration, high elasticity, adhesiveness, and low solubility)
      • Two major mucins (MG1 and MG2)
      Mucus secretion proteins
    • Mucin Functions
      • Lubrication &Visco-elasticity
      • Tissue coating (protection)
      • Aggregation of bacterial cells
        • Bacterial adhere to mucins may result in surface attachment, or
        • Mucin-coated bacteria may be unable to attach to surface
      • Bacterial adhesion
        • Mucin oligosaccharides mimic those on mucosal cell surface
        • React with bacterial adhesins, thereby blocking them
      • (2) Statherins
      • Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid
      • Lubrication and viscosity
      • (3) Proline-rich Proteins
      • 40% of amino acid s is proline , Subdivided into three groups (acidic, basic, glycosylated)
      • Inhibitors of calcium phosphate crystal growth
      • (5) Anti-microbial proteins
      • 1- Lactoferrin
      • Iron-binding protein
      • Some microorganisms (e.g., E. coli ) have adapted to this mechanism by producing enterochelins .
      • 2-Histatins
      • A group of small histidine-rich proteins
      • Protent inhibitors of Candida albicans growth
      • 3- Lysozyme ( muramidase )
      • Present in numerous organs and most body fluids
      • hydrolysis of  (1-4) bond between N-acetylmuramic acid and N-acetylglucosamine in the peptidoglycan layer of bacteria .
        • Gram negative bacteria generally more resistant than gram positive because of outer lipid phosphate layer.
      • 4- Cystatins
      • Are inhibitors of cysteine-proteases
      • Considered to be protective against unwanted proteolysis
        • bacterial proteases
        • lysed leukocytes
      • They inhibit proteases in periodontal tissues
      • They affect on calcium phosphate precipitation
      • 5- Salivary peroxidases
      • Sialoperoxidase (SP, salivary peroxidase)
        • Produced in acinar cells of parotid glands
        • Also present in submandibular saliva
        • Readily adsorbed to various surfaces of mouth
          • enamel, salivary sediment, bacteria, dental plaque
      • Myeloperoxidase (MP)
        • From leukocytes entering via gingival crevice
        • 15-20% of total peroxidase in whole saliva
      • 6- Secretory Immunoglobulins
      • Immunoglobulin A (IgA) is an antibody secreted by mucosal linings in mucous secretions.
      • IgA has two subclasses (IgA1 and IgA2) and can exist in a dimeric form called secretory IgA (sIgA).
      • The secretory component of sIgA protects the immunoglobulin from the being degraded by proteolytic enzymes
      • It plays a critical role in mucosal immunity.