Saliva Composition

Question 1

total % secretion by 3 major glands are..

Answer 1

submandibular= 70%
parotid= 25%
sublingual= 5%

Question 2

types of secretion by 3 major glands are…

Answer 2

submandibular= sero-mucin 
parotid= serous (protein)
sublingual= mucin (mucous)

Question 3

on an average day how much saliva is secreted

Answer 3

1,500 mL/day

Question 4

structure of salivary glands

Answer 4

1. secretory epithelial cells arranged into a bundle=acini
2. acini cells surrounded by myoepithelial cells
3. the intercalated duct connects the acinus with the striated duct
4. secondary modification occurs in striated duct
5. excretory duct= saliva secreted

Question 5

function of myoepithalial cells

Answer 5

contain SMOOTH muscle which contracts= alters the flow rate of saliva

Question 6

ionic composition of saliva compared to plasma …

Answer 6

HCO3- and K+ HIGHER in saliva than plasma

Na+ and Cl- LOWER in saliva than plasma

Question 7

saliva is initially ___, as its composition changes, it becomes ____

Answer 7

initially isotonic - primary secretion

hypotonic- secondary secretion. more ions less water

Question 8

na entry and exit in salivary ducts..

Answer 8

na enters across apical membrane via:

• ENac Na+ transoprter
• Na-H exchanger

na exits across the basolateral membrane via:
-Na-k pump

Question 9

Cl- enter and exit in salivary ducts

Answer 9

cl- enters across apical membrane via:
- Cl-HCO3 exchanger

more cl- exists across basolateral membrane, into intersitial fluid via:
-Cl- ion channels

Question 10

Hco3 enter/ exit

Answer 10

enters on basolateral side but dont know how

exits on apical membrane of cell via:
- CL-HCO3 exchanger

Question 11

K+ entry/exit

Answer 11

enters on basolateral side via:
-Na-K pump

exits on apical membrane side via:
-K-H exchanger

Question 12

the final composition of saliva IS DEPENDANT on SALIVA FLOW RATE. why

Answer 12

more time for secondary ductal modification

Question 13

which ion secretion is NOT dependant on saliva flow rate

Answer 13

bicarobonate- it is strongly influenced by STIMULI causing the increased flow rate of saliva thus even at high flow rates, the HCO3 concentration is always high due to its function as a buffer to protect in acidic environments

Question 14

what is the evidence for 2 -stage hypothesis

Answer 14

1. mapping flow rate curves
2. acinar/ intercalated duct micropunctre
3. poly-lysine injection- poison duct, there is no secondary re-absorportion process

Question 15

saliva stimulation is dependant on the autonomic NS. the comopsition is different if stimulation is via para/ sympathetic NS. how?

Answer 15

para: watery saliva with MORE volume
symp: rich in enzymes, but SMALLER volume

Question 16

where in the brain is the salivary centre

Answer 16

hypothalamus- responds to taste, smell, chewing

also have the higher centres which respond to dehydration, fear, mental effort= dry mouth

Question 17

hormones also control saliva secretion. which hormone?

Answer 17

aldosterone

Question 18

which ion in saliva does aldosterone affect

Answer 18

na+

high aldosterone= low salivary na+ 
low aldosterone (addinson's disease)= high salivary na+