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.