GI Secretions (review w/ handout 10/21 11a) Flashcards Preview

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Flashcards in GI Secretions (review w/ handout 10/21 11a) Deck (54)
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1

Salivary Glands

3 pairs of glands: parotid, submandibular and sublingual
Produce a serous (proteinaceous) or mucus product, or both

2

Water in saliva

facilitates taste and dissolution of nutrients, aids in swallowing/speech

3

bicarb in saliva

neutralizes gastric reflux

4

mucins in saliva

lubrication

5

amylase in saliva

starch digestion
breakdown alpha1-4 bonds

6

lysozyme, lactoferrin, IgA
in saliva

lysozyme: pore forming in bacteria
lactoferrin: sequesters iron (prevent bacteria from obtaining it); great loss w/ IBD
secretory IgA: coats proteins to not internalize bacteria

innate and acquired immune protection

7

epidermal and nerve growth factors in saliva

assumed to contrib to mucosal growth and protection

VEGF, etc

8

Salivary gland structure

myoepithelial cells: contractile cells, facilitate secretion into acinus thru intercalated duct and out thru striated duct

Pancreatic gland doesn't have myoepi cells

Acinar cells make the saliva and striated duct cells modify its ionic content

9

Salivary secretions
CNS regulation

regulated by cephalic phase of digestion

can be downregulated by sleep (so you don't aspirate), fatigue, fear

Pressure in mouth can cause increased salivary secretions

Parasymp increases salivary production (vasodilation), secretion from acinus to intercalated, to striated

Octic ganglion and submandibular ganglion, produce ACh, act on parotid and submandibular gland and increased salivary secretion via effects on Acinar secretion and vasodilation

10

Parasymp regulation of salivary secretion

increased acinar cell secretion and vasodilation of blood vessels surrounding the acini (results in protein rich & fluid/ion rich solution)

11

Sympathetic activation of salivary secretion

– increased acinar cell secretion (results in high protein/low fluid solution)

12

how is saliva formed

passive filtration

content and secretion rate dependent on blood flow:
Increased blood flow around the acinus increases the fluid content of saliva by moving ions and water cellularly and paracellularly into the acinar lumen. TJs are leaky in the acinus

99.5% water and 0.5% electrolytes (Na+, Cl-,
K+, HCO3-) and proteins (mucus, enzymes: amylase, lipase, and antibacterial agents: lysozyme & IgA)
Produce 1-2 liters/day

13

Slow flow rate of salivary secretion

At slow flow rate:
Time means more time for reabsorption of Na, Cl, H+ (adjust level of water and solutes) and secretion of K and bicarb

14

High flow rate

salivary secretions
but don't get time to modify contents in striated ducts

More NaCl present
less K, bicarb

15

Goals of ductal cells

NaCl Reabsorption
K+ secretion
Bicarbonate secretion

16

Bicarb

weak base
CO2 is weak acid
acidic pH-->produce more bicarb
basic pH--> produce less bicarb, more CO2

17

K

very little change in K levels in response to flow rate (don't want to lose much)

18

Salivary secretion key points

Acinar secretions are close to isotonic. TJs allow movement of ions and water from the blood.
In duct cells, Na+/K+ ATPase establishes a concentration gradient. Carbonic anhydrase uses H2O and CO2 to produce H+ and HCO3-
At a low rate of flow, duct cells absorb Na+ and Cl- and secrete K+ and HCO3-.
The movement of water in the ducts is restricted by TJs, leaving the saliva hypotonic.
Faster flow rate limits the action of duct cells on ionic/water content
Secretion is modified by ANS (parasympathetic and sympathetic) and the changes in blood flow

19

vomit and saliva

going to vomit? more saliva formation

20

acinar cells produce
(pancreas)

enzymes: proteases, lipases, and amylases

21

ductal cells produce
(pancreas)

bicarbonate solution to help liquefy and neutralize acidic chyme in the duodenum

Pancreatic secretions are locally and neurally regulated

22

Proteases

trypsinogen
chymotrypsinogen
proleastase
procarboxypeptidase A
procarboxypeptidase B

(stored and secreted in inactive forms)

23

Amylolytic enzyme

amylase

24

lipases

lipase
nonspecific esterase
phospholipase A2 (inactive form)

25

nucleases

deoxyribonucleas
ribonuclease

26

other secretory products of pancrease

procolipase (inactive form)

trypsin inhibitors
monitor peptide

27

ACh and regulation of pancreatic secretion

released from the vagus and ENS nerves; stimulates the release of digestive enzymes from acinar cells (mostly cephalic stage)

28

Secretin and regulation of pancreatic secretion

– released from endocrine cells in the proximal small intestines in response to acid levels; stimulates the release of a bicarbonate rich solution from pancreatic duct cells

29

CCK and regulation of pancreatic secretion

released from endocrine cells in the proximal small intestines in response to fats & proteins; stimulates the release of digestive enzymes from acinar cells but has other effects in the duodenum

30

Regulation of neutralization in response ot acid

acid in lumen leads to increased secretion from duodenal mucosa
secretin carried by blood to pancreatic duct cells
leads to increased secretion of aqueous NaHCO3 soln into duodenal luman
(neutralized acid in duodenal lumen)