Salivary and Gastric Secretory Functions

Question 1

How is saliva controled?

Answer 1

Saliva is under

neuronal control

not hormonal

(hormones modify)

Question 2

Where is cabonic anhydrase found?

Answer 2

Saliva, RBC

What is the significance?

Question 3

What is the function of bicarb is saliva?

Answer 3

Bicarbonate minimizes tooth decay (neutralizes bacterial acid)

(HCO3-) neutralizes refluxed gastric acid into lower esophagus (heartburn)

Question 4

What role do ductal cells play in making saliva hypotonic?

Answer 4

Ductal cells are water impermeable, water is not

absorbed along with the solute, water remains

in lumen and saliva is secreted hypotonic relative

to plasma

Question 5

How are rate and composition of saliva related?

Answer 5

Ionic composition of saliva changes as salivary flow rate changes

                              Duct cells modifies the composition of saliva

²At highest flow rates (4 mL/min), final saliva resembles plasma (high Na+, Cl-, low K+)

  as the ductal cells have less time to modify the saliva

²At lowest flow rates (< 1 mL/min), final saliva is dissimilar to plasma (low Na+, Cl-, high K+)

 as saliva has more contact time with ductal cells, more Na+ and Cl- are reabsorbed, which

 decreases  their concentration and more K+ is secreted (hypotonic)

Question 6

How are salivary glands regulated?

Answer 6

vBoth Symp and Parasymp stimulates secretion
vParasymp stimulates more than Symp
vSymp: major b receptors: protein secretion, minor a receptors fluid secretion
vParasymp: major M3 receptors: fluid secretion

Question 7

What is the control for secretion and composition of saliva?

Answer 7

Salivary secretion and composition are controlled solely by the autonomic nervous system, in contrast, other parts of the GI tract include local reflexes and hormonal mechanisms as well

Question 8

What are the clinical correlations?

Answer 8

I dont know go ask Kathleen.

Question 9

What is cobalamine?

What is required for its absorption?

Answer 9

Vit B12

Intrinsic factor

Question 10

Gastric secretion - rate and composition?

Answer 10

Inverse relationship between luminal conc of

H+ and Na+ as a function of the rate of gastric secretion

Question 11

What is the alkaline tide?

Answer 11

vAt low rates of secretion, gastric juice is a solution of NaCl with a small amount of H+ and K+
vSecretion of H+ into the lumen is balanced by secretion of an equal amount of HCO3- into blood
vIncreased pH of venous blood leaving stomach following a meal is alkaline & referred to as alkaline tide
vpH of stomach ~ 1, 4 million times greater than blood pH.

Question 12

What is the direct stimulation of the parietal cell?

Answer 12

ACh released from vagus nerve binds to M3 receptors

• Histamine released from ECL cell binds to H2 receptors
• Gastrin released from G cell binds to CCKB receptors
• All three agonists synergistically stimulate andpotentiate acid secretion from parietal cell

Question 13

What is the indirect stimulation of the parietal cells?

Answer 13

ACh released from vagus nerve binds to M3

receptors on ECL cell and release histamine

-Gastrin released from G cells binds to CCKB

receptors on ECL cell to release histamine

-Histamine released from ECL cell (by action of

ACh & gastrin) binds to H2 receptors on

parietal cell