20. GI secretory products

Question 1

Intrinsic factor - source

Answer 1

Parietal cells

stomach

Question 2

Intrinsic factor - action

Answer 2

Vitamin B12–binding
protein (required for B12
uptake in terminal ileum)

Question 3

Autoimmune destruction

of parietal cells –>

Answer 3

chronic
gastritis and pernicious
anemia.

Question 4

Gastric acid -SOURCE

Answer 4

Parietal cells

stomach

Question 5

Gastric acid - ACTION

Answer 5

dECREASED stomach pH

Question 6

Gastric acid - REGULATION

Answer 6

INCREASED by histamine,
ACh, gastrin
DECREASED by somatostatin,
GIP,
prostaglandin,
secretin

Question 7

Pepsin -SOURCE

Answer 7

Chief cells

stomach

Question 8

Pepsin - ACTION

Answer 8

Protein digestion

Question 9

Pepsin - REGULATION

Answer 9

increased by vagal
stimulation,
local acid

Question 10

Pepsinogen (inactive) is

converted to

Answer 10

pepsin (active) in

the presence of H+.

Question 11

Bicarbonate trapped in

Answer 11

Trapped in mucus that covers

the gastric epithelium.

Question 12

Bicarbonate -SOURCE

Answer 12

Mucosal cells
(stomach,
duodenum,
salivary glands,
pancreas) and
Brunner glands
(duodenum)

Question 13

Bicarbonate - ACTION

Answer 13

Neutralizes acid

Question 14

Bicarbonate -REGULATION

Answer 14

INCREASED by pancreatic
and biliary
secretion with
secretin

Question 15

• In pernicious anemia, destruction of gastric ____ cells leads to deficiency of ____ required for vitamin B12 uptake in the ____.

Answer 15

Parietal; intrinsic factor; terminal ileum

Question 16

• A patient has chronic abdominal pain and numerous peptic ulcers refractory to proton pump inhibitors. What tumor should be suspected?

Answer 16

Gastrinoma, which is a gastrin-secreting tumor that results in high levels of acid secretion

Question 17

• Describe how pepsin is activated.

Answer 17

It is activated by vagal stimulation of increased acid output, which cleaves inactive pepsinogen to active pepsin

Question 18

• What is the primary role of pepsin? What cells secrete it, and where are these cells found?

Answer 18

Functions in protein digestion; secreted by the gastric chief cells

Question 19

• Bicarbonate is secreted by ____ cells and ____ glands; its function is to ____ acid.

Answer 19

Mucosal; Brunner; neutralize

Question 20

• A patient with a gastrinoma can be expected to also have excessive activation of which pro-enzyme?

Answer 20

Pepsinogen (activated by acid, the release of which is stimulated by gastrin)

Question 21

• Produced by these cells found in this organ, pepsinogen becomes pepsin when there is a high acid content in the stomach.

Answer 21

Chief cells of the stomach

Question 22

• Increased levels of what three molecules cause parietal cells to release gastric acid?

Answer 22

Acetylcholine, histamine, and gastrin

Question 23

• Decreased levels of which hormones will cause parietal cells to secrete gastric acid?

Answer 23

Somatostatin, GIP, prostaglandin, secretin

Question 24

• Increased secretin levels increase the secretion of this molecule, whose main purpose is to neutralize acid.

Answer 24

Bicarbonate

Question 25

• Where is bicarbonate typically trapped in the GI system?

Answer 25

Bicarbonate is trapped in the mucus that covers the gastric epithelium

Question 26

• A patient has vitamin B12 deficiency. What part of the GI system could be damaged, impacting vitamin B12 levels?

Answer 26

Parietal cells of the stomach or the terminal ileum (the latter is where vitamin B12 is absorbed as a complex with intrinsic factor)

Question 27

• Where are bicarbonate-secreting mucous glands found? What about bicarbonate-secreting Brunner glands?

Answer 27

Stomach, duodenum, salivary glands, pancreas; duodenum