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Gastroenterology - Physiology > GI secretory products > Flashcards

GI secretory products Flashcards

1
Q

Where is intrinsic factor released?

A

Parietal cells of stomach

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2
Q

What is the action of intrinsic factor?

A

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

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3
Q

What does autoimmune destruction of parietal cells cause?

A

Chronic gastritis and pernicious anemia due to B12 deficiency

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4
Q

Where is gastric acid secreted from?

A

Parietal cells of the stomach

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5
Q

What is the action of of gastric acid?

A

Decrease stomach pH

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6
Q

What stimulates gastric acid release?

A

Histamine, ACh, gastrin

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7
Q

What decreases gastric acid release?

A

Somatostatin, GIP, prostaglandin, secretin

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8
Q

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

A

Gastrinoma: gastrin-secreting tumor

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9
Q

Where is pepsin secreted from?

A

Chief cells of the stomach

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10
Q

What is the actin of pepsin?

A

Protein digestion

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11
Q

What stimulates pepsin release?

A

vagal stimulation, local acid

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12
Q

In what form is pepsin released?

A

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

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13
Q

Where is bicarb secreted from?

A 
Mucosal cells 
(stomach, 
duodenum, 
salivary glands, 
pancreas) and 
Brunner glands 
(duodenum)
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14
Q

What is the function of bicarb?

A

Neutralizes acid

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15
Q

What stimulates the release of bicarb?

A

Secretin increases pancreatic and biliary bicarb secretion

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16
Q

What covers gastric epithelium?

A

HCO3- is trapped in the mucus covering the epithelium

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17
Q

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

A

parietal cells and Chief cells

18
Q

What do parietal cells secrete?

A

Instrinsic factor and Hcl

19
Q

What do chief cells secrete?

A

Pepsinogen

20
Q

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

A

G cells, Mucuous cells, D cells

21
Q

What secretory cells are located in the duodenum?

A

I cells, S cells, K cells

22
Q

How are G cells stimulated by the vagal nerve?

A

With gastrin-releasing-peptide (neurotransmitter)

23
Q

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

A

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

24
Q

Where are ECL cells located?

A

subepithelial cells found in the vicinity of parietal cells

25
Q

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

A

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

26
Q

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

A

H+ + HCO3- –> H2CO3 –> H2O + CO2

27
Q

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

A

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

28
Q

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

A

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

29
Q

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

A

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

30
Q

How does somatostatin decrease acid secretion from parietal cells?

A

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

31
Q

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

A

Low flow, high Cl-

High flow, high HCO3-

32
Q

What is the purpose of pancreatic alpha amylase?

A

Starch digestion

33
Q

In what form is pancreatic alpha amylase secreted?

A

active form

34
Q

What is the purpose of pancreatic lipase?

A

Lipid digestion

35
Q

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

A

Protein digestion. Trypsin, chymotrypsin, elastase, carboxypeptidases

36
Q

How are the pancreatic proteases secreted?

A

As proenzymes known as zymogens

37
Q

What is the function of trypsinogen/trypsin?

A

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

38
Q

What initially converts trypsinogen to trypsin?

A

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

39
Q

Which carbohydrates are absorbed by enterocytes?

A

Monosacchs; glucose, galactose, fructose

40
Q

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

A

SGLT1 (Na+ dependent) takes up glucose and galactose

GLUT-5 takes up fructose

41
Q

What is the D-xylose absorption test?

A

Distinguishes GI mucosal damage from other causes of malabsorption

Gastroenterology - Physiology (3 decks)

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