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Flashcards in Gastric acid physiology Deck (42):
1

What is anterior to the stomach?

Liver

2

What is posterior to the stomach?

pancreas, colon, diaphragm, spleen

3

What marks the caudal aspect of the gastric body?

Incisura angularis

4

What is the fundus in contact with?

hemidiaphragm and the spleen

5

What are the two types of gastric mucosa that you find in the stomach?

Oxyntic gland mucosa and pyloric gland mucosa. The oxyntic gland mucosa is prox 80% and secretes acid into the body and fundus.

The pyloric mucosa is in the antrum (20% of stomach). Here, GASTRIN is synthesized and released.

6

Describe, very basically, the embryological formation of the stomach

1. Dilation of distal foregut
2. Dorsal aspect grows more rapidly=greater curvature
3. Stomach rotates 90 degrees clockwise

7

What does the right vagus innervate?

posterior stomach wall (primordial right side)

8

What does the left vagus innervate?

Anterior stomach wall (primordial left side)

9

What are the five layers of the stomach?

1. Mucosa
2. Lamina Propria
3. Submucosa
4. Muscularis propria
5. Serosa

10

What's in the submucosa?

Connective tissue containing lymph, A/V, enteric plexus, plasma cells

11

What is in the muscularis propria?

3 muscle layers: inner oblique, middle circular, and outer longitudinal

12

What kinds of cells are in the neck?

parietal and mucous neck cells and PRECURSOR cells

13

What kinds of cells are in the base?

Chief cells, Enterochromaffin Like Cells, G and D cells

14

What do precursor cells do?

They migrate upwards < 1week to become surface mucous cells or downwards (>1 week) to become parietal or chief cells

15

What are the motor fxns of the stomach?

Reservoir for food (Fundus/Body)
mixes, grinds food (antrum)
Empties slowly into duodenum (Pylorus)
Pepsinogen secretion

16

What is significant about the cardia?

Trasition zone from squamous to columnar
Shallow gastric pits with more surface mucous cells

17

What is significant about the antrum?

Regulates gastric secretion through Gastrin/Somatostatin

18

What kind of gastric pits do you see in the fundus/body?

DEEP pits
Parietal, Chief cells mostly
Also ECL and D cells

19

What kind of gastric pits cells do you see in the antrum?

INTERMEDIATE pits
Endocrine cells: G and D cells

20

What are the secretions of the fundus and body?

H+
Intrinsic factor
Pepsinogens
Lipase

21

What do chief cells secrete?

Pepsinogen and gastric lipase

22

What happens in an individual parietal cell when it is stimulated?

Tubulovesicles with H/K ATPases attach to the canaliculus, which expands. The exchanger pumps H+ into the canaliculus which releases HCl into the lumen

23

What stimulates the parietal cell?

Acetylcholine
Gastrin (works on ECL)
Histamine (increases cAMP intracellularly, required fro gastrin secretion)

24

How does the parietal cell generate acid

H/K ATPase pumps H out, and K in.
-An open K channel allows K to "recycle" back in and out
-A Cl- pump maintains electroneutrality
-Carbonic anhydrase converts CO2+OH- into HCO3- which diffuses into the plasma

25

What happens to the alkaline tide?

Bicarb is released interstitially to the surface epithelium to buffer the gastric mucosa

26

At low secretion rates, what do you see in the gastric juices?

NaCl. Low Potassium and H+. Looks like interstitial fluid, with some bicarb present.

27

At high secretion rates, what is the composition of gastric juices?

HCl. Levels of Potassium and sodium are low.

28

Concentrations of what ions are higher in gastric juices than plasma?

H+, Cl, and K are higher. Na+ concentration is lower

29

What are components of soluble mucus?

Mucin with disulfide bridges

30

What is insoluble mucous?

Mucous secreted by surface mucous cells in response to physical or chemical stimuli

31

What enhances soluble mucus secretion?

Acetylcholine from vagal nerve stimulation

32

What are the endocrine hormones in gastric acid secretion?

Gastrin
CCK
Secretin
Glucose dependent insulinotropic peptide

33

What disrupts the gastric mucosa?

aspirin, ethanol, NSAIDs, bile salts

34

What are the hormones with paracrine secretion?

somatostatin and histamine

35

What are the neurocrine hormones?

Ach and gastrin releasing peptide

36

What stimulates gastrin release?

Amino acids
Stomach distention
Vagal stimulation by GRP

37

What does gastrin do?

Stimulates acid secretion thru ECL or by releasing histamine which binds to parietal cells
-Directly stimulates parietal cells
-Stimulates mucosal growth
-Stimulates pepsinogen

38

What inhibits gastrin?

LOW pH of stomach and somatostatin

39

What are the phases of acid secretion?

1. Interdigestive (basal diurnal rhythm)
2. Cephalic (thru vagus)
3. Gastric (food in stomach, distention, peptides)
4. Intestinal (digestion products)

40

What are the most important phases of acid secretion?

Gastric (50%)
Cephalic (30%)

41

How does gastrin stimulate acid release by the parietal cell?

Directly
Indirectly by stimulating the ECL cell to release histamine

42

What is an important stimulator in the intestinal phase?

Amino acids stimulate gastrin release
However, Chyme and other eneterogastrones inhibit acid secretion and gastric emptying (GIP, CCK, Secretin)