Oxyntic and pyloric glands, their cells, their secretions Flashcards Preview

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Flashcards in Oxyntic and pyloric glands, their cells, their secretions Deck (35):
1

Oxyntic glands

D cells (somatostatin)
Chief cells (pepsinogen)
Parietal cells (HCL, intrinsic factor)
mucous neck cells
enterochromaffin cells (histamine secreting)


2

Pyloric glands

D cells (somatostatin)
G cells (gastrin)
enterochromaffin cells (histamine secreting)

3

mechanism of HCL secretion by parietal cells

apical domain transporters
internal activity
basal membrane transporters

apical: H-K exchanger ATPase, bringing K in, and pushing H into the lumen

internally, carbonic anhydrase combines CO2+H2O to form H and HCO3

H is then taken BACK out into the lumen by the H-K exchange ATPase


basal side:

Na/K ATPase

HCO3/CL exchanger, brings Cl into the cell from blood

4

omeprazole targets

the H-K ATPase exchanger on the apical membrane of the parietal cell

it secretes H in exchange for K; K is brought from the blood via Na/K ATPase

Cl is brought into the cell by pumping HCO3 into the blood

Cl diffuses out of the apical part of the cell, following H

H and Cl form HCL

omprazole targets the H secretor so HCL cant form in the lumen

5

what kind of "tide" do we find near parietal cells?

the "alkaline tide" across the basal membrane as HCO3 is reabsorbed into the blood

6

Histamine

a paracrine

released by enterochromaffin cells in response to ACh and gastrin hormone

histamine stimulates parietal cell HCL secretion

binds to H2 receptors on parietal cells

7

what receptors does histamine bind to on the parietal cells?

H2 receptors

8

what blocks the receptors that histamine acts on?

cimetidine blocks H2 receptors

9

histamine --- H2 receptor --->

cAMP ---> H secretion through H/K ATPase

10

ACh

stimulates HCL secretion

released from Vagus

11

ACH from the vagus binds to the ____ receptor

M3 mAChR on parietal cells

12

what blocks the the M3 mAChR receptor?

atropine

binding of ACh to M3 leads to IP3/Ca cascade that results in secretion of H/K ATPase activation

ACh indirectly activates ECL cells which release histamine

13

Gastrin

what secretes it, what happens to it

released by G cells in the antrum into the blood, returned to stomach by circulation

binds to CCKb receptors and causes IP3/Ca cascade ---> H/K ATPase activation

indirectly stimulates ECL cells to release histamine


14

CCKb

affinity for gastrin and CCK

15

CCKa

affinity for CCK only

16

gastrin is stimulated by

stomach distention
presence of small peptides and amino acids, and vagus nerve


17

Atropin blocks

vagal stimulation of M3 mAChR receptors, but does not block vagal stimulation of G cells secreting gastrin

18

somatostatin

a paracrine

inhibits HCL

released from D cells, mostly located in antrum

binds to somatostatin receptors (receptor type 2, SSTR2) on parietal cell

binding of somatostatin to its receptor inhibits adenylate cyclase that results in inhibition of H (direct pathway)

indirect pathway: inhibits both histamine released from ECL cells and gastrin release from G cells

19

what inhibitor is used to treat gastric ulcers?

omeprazole

blocks H-K ATPase

20

what inhibitor is used to treat doudenal ulcers?

cimetidine, treats both duodenal, gastric ulcers, gastroesophageal reflux disorders by blocking H2 histamine receptors

21

atropine blocks what and why, but does not block what and why

blocks the M3 mAChR on parietal cells; a DIRECT pw block

does not Gastrin cells because they use GRP receptors

22

Gastric HCL secretion 3 phases

1. cephalic
2. gastric
3. intestinal phase

23

Gastric ulcer

low H
high gastrin levels because H is low
forms primarily because of mucosal barrier is defective
h pylori usually associated with this
diagnostic instrument: urease enzyme

24

Duodenal ulcer

high H
high gastrin levels in response food ingestion
h pylori infection less here, but can spread from stomach and inhibit somatostatin, causing increase

25

Zollinger Ellison Syndrome

usually the result of a tumor in the head of the pancreas secreting gastrin

high H, high Gastrin

26

Exocrine pancreas

makes up around 90% of the pancreas

glands are like salivary glands: acinus with centroacinar and ductal cells

acinus releases enzymes, centroacinar and ductal cells release HCO3

27

Exocrine pancreas innervation: sympathetics AND parasympathetics

sym comes from celiac and superior mesenteric plexuses

parasym: comes from vagus n

vagal pregang synapse at ENS
postgang synapse on the exocrine pancreas

sym: decrease in activity
parasym: increase in activity

contrast to salivary glands where sym and parasym do the same thing

28

High yield question

pancreas secretes which enzymes in their active and inactive form

secretes amylases and lipases in their active form, but proteases in their inactive form

29

centeroacinar and ductal cells release

Na, K, Cl, HCO3

30

when pancreatic flow rate is low, the two highest ions secreted include

chlorine and sodium

31

when pancreatic flow rate is high, the two highest ions secreted include

HCO3 and Na

32

HCO3/CL relationship in pancreatic seretions

reciprocal

33

Cephalic phase of pancreas

same as for salivary glands but results mainly in enzymatic secretion

34

gastric phase of pancreas

like salivary glands but mostly enzymatic secretion

35

intestinal phase of pancreas

like salivary glands but enzymatic AND aqueous secretions