Lecture 22: Salivary + Pancreatic Secretion

Question 1

Salivary glands

Answer 1

Parotid, sublingual, submandibular

Question 2

Functions of saliva

Answer 2

1. Hydration for mastication/deglutition
2. Bicarb secretion
3. Produce R factor for Vit. B12
4. Protect vs bacteria w/ lysozyme, buffers, IgA
5. Initiate food digestion (lingual amylase, lipase)

Question 3

Salivary α-amylase (ptayalin)

Answer 3

Cleaves α-1,4 glycosidic bonds in interior of molecules, optimal pH = 6.7

Question 4

Cells involved in salivary secretion

Answer 4

Initial saliva secreted by acinar cells (myoepithelial cells squeeze out); ductal cells modify

Question 5

Salivary acinar cell secretion method

Answer 5

H2O + Na+ follow Cl- into lumen. K+ leak drives Na+/K+ exchanger, Cl- import

Question 6

Saliva modification by ductal cells mechanism

Answer 6

Active Na+, Cl- absorption; K+, bicarb secretion. Duct is H2O impermeable; saliva becomes hypotonic

Question 7

Flow rate effect on ionic saliva composition

Answer 7

Concentration modification depends on time saliva contacts ductal cells; more contact time -> more hypotonic

Question 8

Exception to flow rate effect on saliva

Answer 8

Bicarb; bicarb secretion selectively stimulated when saliva production is (both symp. + parasymp.)

Question 9

Regulation of saliva secretion

Answer 9

Saliva secretion exclusively under ANS neural control (symp. + parasymp., parasymp. dominates)

Question 10

What does neural stimulation of the salivary glands do?

Answer 10

Stimulation increases blood flow to salivary glands e.g. bradykinin vasodilation.
Increase in cap. P -> more H2O/electrolyte filtration -> more saliva

Question 11

Pancreatic secretion phases

Answer 11

1. Cephalic
2. Gastric
3. Intestinal

Question 12

Cephalic phase pancreatic secretion

Answer 12

Vagal efferent stim. -> some enzyme/bicarb secretion
Vagal stim. -> minor gastrin secretion -> pancreatic secretion augment.

Question 13

Intestinal phase pancreatic secretion

Answer 13

AAs/peptides/FAs/duodenal acid load stim. vaso-vagal reflex, CCK/secretin release -> huge increase in enzyme/bicarb secretion

Question 14

CCK stimulation of pancreas

Answer 14

Direct: stim. enzyme/bicarb secretion
Indirect: stim. vaso-vagal reflex -> more pancreatic secretion
CCK potentiates ductal cell secretion

Question 15

I cells

Answer 15

Secrete CCK in response to AAs/small peptides/FAs in intestine; acinar cell stim. via IP3/Ca2+ for enzymes

Question 16

S cells

Answer 16

Secrete secretin in response to intestinal acid; ductal cell stim. via cAMP for aqueous bicarb secretion (Na+, bicarb)

Question 17

Intestinal phase pancreatic secretion synergy

Answer 17

ACh, CCK, secretin have synergy and potentiate each other to increase pancreatic enzyme/bicarb output

Question 18

Pancreatic duct cell secretion mechanism

Answer 18

• Bicarb is both imported and produced
• Acid tide
• CFTR; Na+, H2O follow Cl-
• CFTR countered by bicarb secretion

Question 19

Flow rate effect on pancreatic juice composition

Answer 19

Low Q: pancreas juice has more Na+, Cl-
Higher Q: pancreas juice has more Na+, bicarb e.g. secretin stimulation

Question 20

Pancreatic proteases

Answer 20

Produced and secreted as zymogens

Question 21

Pancreatic Secretory Trypsin Inhibitory

Answer 21

Further protects pancreas from autodigestion

Question 22

Activating enterokinase

Answer 22

Found on enterocyte brush border to activate trypsinogen; anatomically separate from secretion site

Question 23

Acinar pancreatic enzyme synthesis process

Answer 23

1/2. RER synthesis
3. Proteins sorted to Golgi
4. Secretory/condensing vacuole packaging
5. Zymogen concentration in granules w/ PSTI
6. Secretory stimulation causes zymogen granules to fuse w/ membrane

Question 24

Acute pancreatitis

Answer 24

Causes: ischemia, obstruction, alcohol leading to premature zymogen activation
Induces acinar necrosis/autodigestion; proteases escape to EC space and cause inflammation