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Secretory Function of GIT
Salivary secretion Gastric juice secretion Pancreatic juice Biliary secretion 14-Nov-18 salivary secretion
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Salivary Secretion Functions of saliva Salivary glands
Composition of saliva Secretory process Control mechanism 14-Nov-18 salivary secretion
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Functions of Saliva Moisten and lubricate food Dissolve food Digestion
Taste buds can be stimulated Digestion Salivary amylase Oral health Washes food particles Prevent dental carries Lysozymes – antibacterial 14-Nov-18 salivary secretion
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Salivary Glands Parotid gland Serous gland Watery secretion
Protein – salivary amylase Electrolytes Produces 20% of total saliva 14-Nov-18 salivary secretion
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Salivary Glands Submandibular glands Mixed glands
Secrete both mucus and serous secretions Electrolytes, mucus, protein Produce 70% of total saliva 14-Nov-18 salivary secretion
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Salivary Glands Sublingual Others Mucous Secrete mucus
Produces 5% of total saliva Others Bucal glands, lingual Minor produce mucus Produce 5% of total saliva 14-Nov-18 salivary secretion
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Physiological Anatomy
Secretory function of salivary gland Salivon Acinus Duct system Arterial blood supply (counter current) 14-Nov-18 salivary secretion
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Functional unit of salivary gland
Acinar capillaries Acinus Blood flow Intercalated ducts Duct capillaries Interlobular ducts Excretory duct Salivary flow 14-Nov-18 salivary secretion
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Composition of Saliva Electrolyte
Na+, K+, HCO3-, Cl- Urea, Iodide Water Saliva is hypotonic in comparison to plasma Contain higher potassium & bicarbonate Lower sodium and chloride 14-Nov-18 salivary secretion
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Composition Proteins Volume of saliva = 500 to 1500 ml/24 hrs
Enzymes (ptyalin, lingual lipase) Plasma proteins “R” proteins – cobalmin binding Mucin – glycoprotein lubricate food Volume of saliva = 500 to 1500 ml/24 hrs 14-Nov-18 salivary secretion
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Composition Composition of saliva changes with rate of secretion
At low rate of secretion Osmolarity is very low; As low as 50 mOsm/l At maximum rate Composition approaches that of plasma 300 mOsm/l 14-Nov-18 salivary secretion
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Secretory Process Saliva secretion involves two processes
Primary secretion by acinus Secondary modification by salivary ducts 14-Nov-18 salivary secretion
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Primary Process Acinus secrete primary secretion that contain
Na+, Cl-, H2O, HCO3-, protein, mucin Acinus secrete primary secretion that contain Protein, mucin, electrolyte, water in conc. Similar to that of ECF Ultra-filtrate of plasma 14-Nov-18 salivary secretion
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Primary Process Protein Mucin Serum protein (0.1 to 0.5 gm/dl)
Na+, Cl-, H2O, HCO3-, protein, mucin Protein Serum protein (0.1 to 0.5 gm/dl) Immunoglobin A Salivary α amylase Mucin Glycoprotein, mucopolysaccharide Blood group specific 14-Nov-18 salivary secretion
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Secondary Modification
Na+, Cl-, H2O, HCO3-, protein, mucin As the primary secretion flows through the duct system Secretion of some substances in the duct HCO3- , K+, Cl-, Urea, Iodide Reabsorption of materials from the duct Na+ HCO3-, urea, Iodide Na+ K+ Cl- Na+, Cl-, H2O, HCO3-, proteins, Urea, Iodide ,K+ 14-Nov-18 salivary secretion
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Secondary Modification
Na+, Cl-, H2O, HCO3-, protein, mucin Under resting condition Conc. Of Na+ = 15 mEq/l About 1/10 that of plasma Conc. Of K+ = 30 mEq/l About 7 times that of plasma HCO3-, urea, Iodide Na+ K+ Cl- Na+, Cl-, H2O, HCO3-, proteins, Urea, Iodide ,K+ 14-Nov-18 salivary secretion
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Secondary Modification
Na+, Cl-, H2O, HCO3-, protein, mucin Conc. Of HCO3- = 50 to 70 mEq/L About 2 to 3 times that of plasma pH 5.45 to 6.06 HCO3-, urea, Iodide Na+ K+ Cl- Na+, Cl-, H2O, HCO3-, proteins, Urea, Iodide ,K+ 14-Nov-18 salivary secretion
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Secondary Modification
Na+, Cl-, H2O, HCO3-, protein, mucin During maximal stimulation Increased rate of formation of primary secretion Rapid flow of fluid Little modification Electrolyte Na+, Cl- rises to about ½ to 2/3rd that of plasma K+ conc. Falls HCO3- conc. Rises PH 6.0 to 7.4 HCO3-, urea, Iodide Na+ K+ Cl- Na+, Cl-, H2O, HCO3-, proteins, Urea, Iodide ,K+ 14-Nov-18 salivary secretion
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Secondary Modification
Na+, Cl-, H2O, HCO3-, protein, mucin Aldosterone increase Na+ re-absorption K+ secretion HCO3-, urea, Iodide Na+ K+ Cl- Na+, Cl-, H2O, HCO3-, proteins, Urea, Iodide ,K+ 14-Nov-18 salivary secretion
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14-Nov-18 salivary secretion
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Control of Salivary Secretion
Controlled by ANS Parasympathetic Cause gland cells to secrete large volume of watery fluid High in electrolytes Low in protein There is profound vasodilatation Due to release of VIP A co-transmitter with Ach Atropine block Ach block Ach Reduces saliva secretion 14-Nov-18 salivary secretion
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Control of salivary secretion
Sympathetic Causes gland cells to secrete small volume of fluid High concentration of mucus 14-Nov-18 salivary secretion
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- IX VII Higher centers Salivary nucleus
Fear, sleep, fatigue, dehydration Thought, Sight, Smell, taste, Appetite center Salivary nucleus IX Parotid VII Stomach, Intestine Sublingual Submandibular 14-Nov-18 salivary secretion
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