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FA - Gastrointestinal > GI - Physiology (GI Secretions) > Flashcards

GI - Physiology (GI Secretions) Flashcards

Pg. 346-347 in First Aid 2014 Sections include: -GI secretory products -Locations of GI secretory cells -Gastric parietal cell -Brunner glands -Pancreatic secretions

1
Q

What are 4 GI secretory products?

A

(1) Intrinsic factor (2) Gastric acid (3) Pepsin (4) HCO3-

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2
Q

What cells are the source of Intrinsic factor, and in what part of the GI system are they located?

A

Parietal cells (stomach)

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3
Q

What cells are the source of gastric acid, and in what part of the GI system are they located?

A

Parietal cells (stomach)

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4
Q

What 2 secretory products do parietal cells produce? Where are they located?

A

(1) Intrinsic factor (2) Gastric acid; Parietal cells (stomach)

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5
Q

What cells are the source of Pepsin, and in what part of the GI system are they located?

A

Chief cells (stomach)

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6
Q

What cells are the source of HCO3-, and in what part of the GI system are they located?

A

(1) Mucosal cells (stomach, duodenum, salivary glands, pancreas) and (2) Brunner glands (duodenum)

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7
Q

What is the action of Intrinsic factor?

A

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

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8
Q

What 2 conditions can be caused by autoimmune destruction of parietal cells?

A

Autoimmune destruction of parietal cells –> chronic gastritis and pernicious anemia

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9
Q

What is the action of Gastric acid?

A

Decreases stomach pH

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10
Q

What factors regulate Gastric acid production, and in what ways?

A

INCREASE: by histamine, ACh, gastrin; DECREASE: by somatostatin, GIP, prostaglandin, secretin

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11
Q

What is a Gastrinoma? What physiological and medical consequences does it have?

A

Gastrinoma: gastrin-secreting tumor that causes high levels of acid secretion and ulcers refractory to medical therpay

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12
Q

What is the action of Pepsin?

A

Protein digestion

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13
Q

What factors regulate Pepsin, and in what way?

A

INCREASED by vagal stimulation, local acid

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14
Q

What is the precursor for Pepsin, and how is it activated?

A

Inactive pepsinogen –> pepsin by H+

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15
Q

What is the function of HCO3- in the GI system?

A

Neutralizes acid

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16
Q

What factors regulate HCO3- secretion in the GI system, and in what way?

A

INCREASED by pancreatic and biliary secretion with secretin

17
Q

Where is HCO3- trapped in the GI tract?

A

HCO3- is trapped in mucus that covers the gastric epithelium

18
Q

On what site does gastrin act mostly, and what effects does this have?

A

Gastrin increases acid secretion through its effects on enterochromaffin-like (ECL) cells (leading to histamine release) rather than through its direct effect on parietal cells

19
Q

What is the action of Atropine on GI secretion? What is major regulatory factor of GI secretion is unaffected, and why?

A

Atropine blocks vagal stimulation of parietal cells. Vagal stimulation of G cells is unaffected, as a different transmitter (gastrin-releasing peptide, or GRP) is used, not ACh

20
Q

What are 3 GI secretory cells below the pyloric sphincter and their products?

A

(1) I cells - CCK (2) S cells - Secretin (3) K cells - GIP

21
Q

What are 3 GI secretory cells in the antrum of the stomach and their products?

A

(1) D cells - Somatostatin (2) Mucous cells - Mucus (3) G cells - Gastrin

22
Q

What are 3 GI secretory cells in the body of the stomach and their products?

A

(1) Parietal cells - HCl, Intrinsic factor (2) ECL cells - Histamine (3) Chief cells - Pepsinogen

23
Q

What are 3 stimulators of gastric parietal cells & their mechanisms? What is the most important mechanism of gastric parietal cell stimulation?

A

(1) ACh - ACh from vagus, signals through M3 receptor and Gq to promote H/K pump (2) Gastrin - G cells activated by GRP from Vagus to release gastrin, which signals through CCK receptor and Gq to promote H/K pump (3) Histamine - Gastrin from from G cells stimulates ECL cells (most important mechanism) to release histamine, which signals through H2 receptors and Gs to promote H/K pump

24
Q

What are 2 inhibitors of the gastric parietal cell gastric acid secretion? What is their mechanism?

A

(1) Prostaglandins/Misoprostol (2) Somatostatin; Signal through Gi to inhibit H/K pump

25
Q

What is considered to be the “alkaline tide” of a gastric parietal cell? Draw the explanation.

A

See p. 347 in First Aid 2014 for visual at top of page

26
Q

Draw the relation of carbonic anhydrase to the H/K pump in gastric parietal cells.

A

See p. 347 in First Aid 2014 for visual at top of page

27
Q

Where are Brunner glands located? What function do they serve?

A

Located in duodenal submucosa. Secrete alkaline mucus.

28
Q

In what condition is hypertrophy of Brunner glands seen?

A

Hypertrophy seen in peptic ulcer disease

29
Q

What tonicity does pancreatic secretion fluid have?

A

Isotonic fluid

30
Q

How does the flow rate of pancreatic secretions relate to change in ion concentrations?

A

Low flow => High Cl-; High flow => High HCO3-

31
Q

What are 4 kinds of pancreatic secretions?

A

(1) Alpha-amylase (2) Lipase, phospholipase A, colipase (3) Proteases (4) Trypsinogen

32
Q

What is the role of alpha-amylase? In what form is it secreted?

A

Starch digestion; Secreted in active form

33
Q

What is the role of lipase? What are the specific names of 2 other enzymes in pancreatic secretions that share this role?

A

Fat digestion; Lipase, Phospholipase A, Colipase

34
Q

What is the role of Proteases? In what form are they secreted?

A

Protein digestion; Secreted as proenzymes also known as zymogens

35
Q

What are 4 examples of Proteases?

A

Includes (1) trypsin, (2) chymotrypsin, (3) elastase, (4) carboxypeptidases

36
Q

To what is trypsinogen converted? What role(s) does this product play?

A

Converted to active enzyme trypsin => Activation of other proenzymes and cleaving of additional trypsinogen molecules into active trypsin (positive feedback loop)

37
Q

What enzyme converts trypsinogen to trypsin? Where is this enzyme found?

A

Trypsinogen converted to trypsin by Enterokinase/Enteropeptidase, a brush-border enzyme on the duodenal and jejunal mucosa

FA - Gastrointestinal (24 decks)

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