GI secretory products

Question 1

Where is intrinsic factor released?

Answer 1

Parietal cells of stomach

Question 2

What is the action of intrinsic factor?

Answer 2

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

Question 3

What does autoimmune destruction of parietal cells cause?

Answer 3

Chronic gastritis and pernicious anemia due to B12 deficiency

Question 4

Where is gastric acid secreted from?

Answer 4

Parietal cells of the stomach

Question 5

What is the action of of gastric acid?

Answer 5

Decrease stomach pH

Question 6

What stimulates gastric acid release?

Answer 6

Histamine, ACh, gastrin

Question 7

What decreases gastric acid release?

Answer 7

Somatostatin, GIP, prostaglandin, secretin

Question 8

What should be suspected in a pt w/ high levels of acid and ulcers refractory to medical therapy?

Answer 8

Gastrinoma: gastrin-secreting tumor

Question 9

Where is pepsin secreted from?

Answer 9

Chief cells of the stomach

Question 10

What is the actin of pepsin?

Answer 10

Protein digestion

Question 11

What stimulates pepsin release?

Answer 11

vagal stimulation, local acid

Question 12

In what form is pepsin released?

Answer 12

Pepsinogen, which is converted to pepsin (Active) int he presence of H+

Question 13

Where is bicarb secreted from?

Answer 13

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

Question 14

What is the function of bicarb?

Answer 14

Neutralizes acid

Question 15

What stimulates the release of bicarb?

Answer 15

Secretin increases pancreatic and biliary bicarb secretion

Question 16

What covers gastric epithelium?

Answer 16

HCO3- is trapped in the mucus covering the epithelium

Question 17

Which secretory cells are located in the body of the stomach?

Answer 17

parietal cells and Chief cells

Question 18

What do parietal cells secrete?

Answer 18

Instrinsic factor and Hcl

Question 19

What do chief cells secrete?

Answer 19

Pepsinogen

Question 20

What secretory cells are located in the antrum of the stomach?

Answer 20

G cells, Mucuous cells, D cells

Question 21

What secretory cells are located in the duodenum?

Answer 21

I cells, S cells, K cells

Question 22

How are G cells stimulated by the vagal nerve?

Answer 22

With gastrin-releasing-peptide (neurotransmitter)

Question 23

How do G cells secreting gastrin in the antrum lead to increase H+ secretion in the body?

Answer 23

Gastrin goes to circulation, interacts with ECL cells, which secrete histamine. Histamine stimulates acid release from parietal cells.

Question 24

Where are ECL cells located?

Answer 24

subepithelial cells found in the vicinity of parietal cells

Question 25

How does Ach transmit an acid releasing signal to parietal cells?

Answer 25

Ach arrivs at M3 receptor Gq --> Ca2+ Activation of ATPase H+/K+

Question 26

Where does the secreted H+ from the parietal cell come from?

Answer 26

H+ + HCO3- --> H2CO3 --> H2O + CO2

Question 27

How does Gastrin directly transmit an acid releasing signal to parietal cells?

Answer 27

GRP arrives at G cells--> gastrin, Gastrin arrivs at CCK8 receptor of parietal cell Gq --> Ca2+ Activation of ATPase H+/K+

Question 28

How does gastrin indirectly cause an increase in acid secretion from parietal cells?

Answer 28

Gastrin --> ECLs-->secrete histamine Histamine arrvs at H2 receptor H2 receptor associated with Gs --> cAMP

Question 29

How do prostaglandins and misoprostol decrease acid secretion from parietal cells?

Answer 29

Arrive at receptor, interact with Gi, decr cAMP, decrease activity of H+/K+ ATPase.

Question 30

How does somatostatin decrease acid secretion from parietal cells?

Answer 30

Arrives at receptor, interact with Gi, decr cAMP, decrease activity of H+/K+ ATPase.

Question 31

What is the Cl- vs. HCO3- content in pancreatic secretions?

Answer 31

Low flow, high Cl- | High flow, high HCO3-

Question 32

What is the purpose of pancreatic alpha amylase?

Answer 32

Starch digestion

Question 33

In what form is pancreatic alpha amylase secreted?

Answer 33

active form

Question 34

What is the purpose of pancreatic lipase?

Answer 34

Lipid digestion

Question 35

What is the purpose of pancreatic protease secretion? What are the proteases?

Answer 35

Protein digestion. Trypsin, chymotrypsin, elastase, carboxypeptidases

Question 36

How are the pancreatic proteases secreted?

Answer 36

As proenzymes known as zymogens

Question 37

What is the function of trypsinogen/trypsin?

Answer 37

Active trypsin activates other proenzymes and cleaves additional trypsinogens into active trypsin (postive feedback loop)

Question 38

What initially converts trypsinogen to trypsin?

Answer 38

Enterokinase/enteropeptidase, a brush border enzyme on duodenal and jejunal mucosa

Question 39

Which carbohydrates are absorbed by enterocytes?

Answer 39

Monosacchs; glucose, galactose, fructose

Question 40

What transporters take up glucose, galactose and fructose into the enterocyte?

Answer 40

SGLT1 (Na+ dependent) takes up glucose and galactose | GLUT-5 takes up fructose

Question 41

What is the D-xylose absorption test?

Answer 41

Distinguishes GI mucosal damage from other causes of malabsorption