1. Secretory Function of GIT
Salivary secretion
Gastric juice secretion
Pancreatic juice
Biliary secretion
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2. Salivary Secretion Functions of saliva Salivary glands
Composition of saliva
Secretory process
Control mechanism
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3. 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
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4. Salivary Glands Parotid gland Serous gland Watery secretion
Protein – salivary amylase
Electrolytes
Produces 20% of total saliva
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5. Salivary Glands Submandibular glands Mixed glands
Secrete both mucus and serous secretions
Electrolytes, mucus, protein
Produce 70% of total saliva
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6. Salivary Glands Sublingual Others Mucous Secrete mucus
Produces 5% of total saliva
Others
Bucal glands, lingual
Minor produce mucus
Produce 5% of total saliva
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7. Physiological Anatomy
Secretory function of salivary gland
Salivon
Acinus
Duct system
Arterial blood supply (counter current)
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8. Functional unit of salivary gland
Acinar capillaries
Acinus
Blood flow
Intercalated ducts
Duct capillaries
Interlobular ducts
Excretory duct
Salivary flow
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9. 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
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10. 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
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11. 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
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12. Secretory Process Saliva secretion involves two processes
Primary secretion by acinus
Secondary modification by salivary ducts
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13. 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
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14. 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
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15. 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+
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16. 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+
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17. 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+
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18. 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+
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19. 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+
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21. 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
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22. Control of salivary secretion
Sympathetic
Causes gland cells to secrete small volume of fluid
High concentration of mucus
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23.  -  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
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