Saliva secretion

1. 29-Apr-24 salivary secretion 1
Secretory Function of
GIT
Salivary secretion
Gastric juice secretion
Pancreatic juice
Biliary secretion

2. 29-Apr-24 salivary secretion 2
Salivary Secretion
 Functions of saliva
 Salivary glands
 Composition of saliva
 Secretory process
 Control mechanism

3. 29-Apr-24 salivary secretion 3
Functions of Saliva
 Moisten and lubricate food
 Dissolve food
– Taste buds can be stimulated
 Digestion
– Salivary amylase
 Oral health
– Washes food particles
– Prevent dental carries
– Lysozymes – antibacterial

4. 29-Apr-24 salivary secretion 4
Salivary Glands
 Parotid gland
– Serous gland
– Watery secretion
• Protein – salivary amylase
• Electrolytes
– Produces 20% of total saliva

5. 29-Apr-24 salivary secretion 5
Salivary Glands
 Submandibular glands
– Mixed glands
– Secrete both mucus and serous
secretions
• Electrolytes, mucus, protein
– Produce 70% of total saliva

6. 29-Apr-24 salivary secretion 6
Salivary Glands
 Sublingual
– Mucous
– Secrete mucus
– Produces 5% of total saliva
 Others
– Bucal glands, lingual
• Minor produce mucus
– Produce 5% of total saliva

7. 29-Apr-24 salivary secretion 7
Physiological Anatomy
 Secretory function of salivary
gland
– Salivon
• Acinus
• Duct system
• Arterial blood supply (counter current)

8. 29-Apr-24 salivary secretion 8
Acinar capillaries
Duct
capillaries
Acinus
Intercalated ducts
Interlobular ducts
Excretory duct
Functional unit of
salivary gland
Blood
flow
Salivary flow

9. 29-Apr-24 salivary secretion 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

10. 29-Apr-24 salivary secretion 10
Composition
 Proteins
– Enzymes (ptyalin, lingual lipase)
– Plasma proteins
– “R” proteins – cobalmin binding
– Mucin – glycoprotein lubricate food
 Volume of saliva = 500 to 1500
ml/24 hrs

11. 29-Apr-24 salivary secretion 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

12. 29-Apr-24 salivary secretion 12
change in concentration of salivary electrolyte
with rate of flow
0
50
100
150
1 2 3 4 5
flow of saliva ml/min
mEq
l/
L
Na+
K+
HCO3-
CL-

13. 29-Apr-24 salivary secretion 13
Secretory Process
 Saliva secretion
involves two
processes
– Primary secretion
by acinus
– Secondary
modification by
salivary ducts

14. 29-Apr-24 salivary secretion 14
Primary Process
 Acinus secrete
primary
secretion that
contain
– Protein, mucin,
electrolyte, water
in conc. Similar to
that of ECF
• Ultra-filtrate of
plasma
Na+, Cl-, H2O,
HCO3
-, protein,
mucin

15. 29-Apr-24 salivary secretion 15
Primary Process
 Protein
– Serum protein (0.1 to
0.5 gm/dl)
– Immunoglobin A
– Salivary α amylase
 Mucin
– Glycoprotein,
mucopolysaccharide
– Blood group specific
Na+, Cl-, H2O,
HCO3
-, protein,
mucin

16. 29-Apr-24 salivary secretion 16
Secondary Modification
 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+
Na+, Cl-, H2O,
HCO3
-, protein,
mucin
HCO3
-, urea,
Iodide
Na+
K+
Cl-
Na+, Cl-, H2O, HCO3
-,
proteins, Urea,
Iodide ,K+

17. 29-Apr-24 salivary secretion 17
Secondary Modification
 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
Na+, Cl-, H2O,
HCO3
-, protein,
mucin
HCO3
-, urea,
Iodide
Na+
K+
Cl-
Na+, Cl-, H2O, HCO3
-,
proteins, Urea,
Iodide ,K+

18. 29-Apr-24 salivary secretion 18
Secondary Modification
– Conc. Of
– HCO3
- = 50 to 70
mEq/L
• About 2 to 3 times
that of plasma
– pH 5.45 to 6.06
Na+, Cl-, H2O,
HCO3
-, protein,
mucin
HCO3
-, urea,
Iodide
Na+
K+
Cl-
Na+, Cl-, H2O, HCO3
-,
proteins, Urea,
Iodide ,K+

19. 29-Apr-24 salivary secretion 19
Secondary Modification
 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
Na+, Cl-, H2O,
HCO3
-, protein,
mucin
HCO3
-, urea,
Iodide
Na+
K+
Cl-
Na+, Cl-, H2O, HCO3
-,
proteins, Urea,
Iodide ,K+

20. 29-Apr-24 salivary secretion 20
Secondary Modification
 Aldosterone
increase
– Na+ re-
absorption
– K+ secretion
Na+, Cl-, H2O,
HCO3
-, protein,
mucin
HCO3
-, urea,
Iodide
Na+
K+
Cl-
Na+, Cl-, H2O, HCO3
-,
proteins, Urea,
Iodide ,K+

21. 29-Apr-24 salivary secretion 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

22. 29-Apr-24 salivary secretion 22
Control of salivary
secretion
 Sympathetic
– Causes gland cells to secrete small
volume of fluid
• High concentration of mucus

23. 29-Apr-24 salivary secretion 23
Higher
centers
Salivary
nucleus
IX
VII
Parotid
Sublingual
Submandibular
Stomach,
Intestine
Thought, Sight,
Smell, taste,
Fear, sleep,
fatigue,
dehydration
Appetite
center
-
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