2.06 GI Secretions & Asorption

Question 1

How is the stomach antrum different from the corpus/body in terms of what cells it has?

Answer 1

No parietal cells
Endocrine Cells

Question 2

What does gastric fluid look like in a low secretion or low gastric acid state?

Answer 2

Resembles plasma electrolyte composition (pH 6-7)
High Na+ and Low H+ b/c non parietal cells

Question 3

What does gastric fluid look like in a high gastric acid or high secretion state?

Answer 3

Low pH (1-2), H+ secreted by parietal cells (HCL) rather than NaCl , b/c increase in gastrin and Histamine signaling

Question 4

What does the parietal cells have that allows it to increase its surface are when cell is stimulated?

Answer 4

Tubulovesicular structures (canaliculus when active)

Question 5

Where do the H+ ions pumped out by the parietal cells come from?

Answer 5

Passive uptake of CO2 and H20 (OH) that gets converted by carbonic anhydride to HCO3- (bicarb/Cl- exchanger) and H+

Question 6

What helps regulate parietal cell pH levels at the basal state?

Answer 6

Na-H exchanger

Question 7

What are three things that acts synergistically to release H+ from parietal cells?

Answer 7

Ach
Histamine
Gastrin

Question 8

Where does Ach come from and bind to directly act on parietal cells?

Answer 8

Ach from vagus binds to M3 receptor

Question 9

Where does gastrin come from and what does it bind to in order to directly stimulate parietal cells?

Answer 9

Gastrin from G cells to CCK2 receptor

Question 10

Where does Histamine come from and what does it bind to in order to active parietal cells?

Answer 10

His from ECL cell binds to H2 receptor

Question 11

What are H2 blockers that act as competitive antagonists to block Histamine?

Answer 11

Cimetidine & Ranitidine

Question 12

What are indirect ways to activate the parietal cell?

Answer 12

All through the ECL cells
Ach to M3 to release His
Gastrin to CCK2 to release His

Question 13

Condition that results in gastric hypersecretion that can lead to peptic ulcers and gastrinomas?

Answer 13

Zollinger Ellison Syndrome

Question 14

How does high gastrin both directly and indirectly acts on pathways?

Answer 14

Direct = CCK2 on parietal
Indirect = ECL stimulation

Question 15

What is the endocrine cels responsible for relabeling gastrin?

Answer 15

G cells

Question 16

What is the endocrine cell responsible for the inhibition of gastrin release?

Answer 16

D cell

Question 17

What are the stimuli for gastrin release?

Answer 17

Food (luminal peptides and amino acids) and Neuronal (direct vagal or D cells)

Question 18

What is the stimuli for the inhibition of gastrin?

Answer 18

Gastrin activates CCK2 on C cells and stimulated tor release Somatostatin that inhibits G cells & partial cells

Question 19

What cells works to inhibit the release of gastrin?

Answer 19

D cells

Question 20

What inhibits the release of somatostatin from D cells?

Answer 20

Ach on M3 receptor (D cells)

Question 21

What is GRP>

Answer 21

Gastrin releasing peptide activated by vagus and directly stimulates G cell

Question 22

The D cell in the antrum has what pathway source?

Answer 22

Endocrine

Question 23

The D cell in the corpus has what pathway source?

Answer 23

Paracrine

Question 24

What is the stimuli that inhibits gastric acid secretion?

Answer 24

Fat, acid, and hyperosmolar solution in the duodenum!

Question 25

What is the most potent stimuli to inhibit gastric acid release?

Answer 25

Fat

Question 26

Where does secretin come from?

Answer 26

S cells from duodenum and jejunum

Question 27

Where does CCK come from?

Answer 27

I cells from duodenum and jejunum

Question 28

Where does gastric inhibitory peptide (GIP) come from?

Answer 28

K cells from duodenum and jejunum response to nutrients

Question 29

Where does peptide YY come from?

Answer 29

L cells in distal intestine

Question 30

What are the direct effects of secretion?

Answer 30

Down regulate H/K atpase pump from parietal cells and inhibit gastrin release form G cells

Question 31

What are teh indirect affects of secretin?

Answer 31

Stimulate D cells to release somatostatin that further inhibits acid secretion

Question 32

What stimulates the release of prostaglandin E2?

Answer 32

Increased luminal acid exposure

Question 33

What does prostaglandin E2 INdirectly do?

Answer 33

Bind to EP3 on BL membrane to inhibit AC and prevent AMP increase and blocked H2 receptor pathway (not receptor) Indirect inhib His and gastrin release

Question 34

What drug activates the EP3 receptor to indirectly inhibit H/K ATPase?

Answer 34

Misoprostol

Question 35

What does ingesting food do to the gastric acid?

Answer 35

Decreases cause it buffers it, it increases as food leaves the stomach to the standard 1-2.5 pH

Question 36

What do chief cells do?

Answer 36

Release pepsinogen (inactive)

Question 37

What converts pepsinogen to pepsin?

Answer 37

HCL

Question 38

When does pepsin become inactive?

Answer 38

When it reaches duodenum cause of higher pH

Question 39

What does pepsin do?

Answer 39

Breakdown proteins into AA at stomach

Question 40

What stimulates chief cells to release pepsinogen?

Answer 40

Ach from vagal, gastrin from G cells, local cholinergic reflex triggered by low pH, secretin from S cells

Question 41

Where is B12 absorbed?

Answer 41

Ilium

Question 42

Where is IF secreted?

Answer 42

Parietal cells

Question 43

Damage to what can contribute to loss of acid secretion and loss of IF?

Answer 43

Parietal cells

Question 44

Unvaccinated child under <5 years with watery diarrhea and viral origin should hint at?

Answer 44

Rotavirus