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The Stomach Flashcards

1
Q 
Which of the following are not functions of the stomach?
Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion
A

Ingestion
Absorption
Excretion

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2
Q

What kind of muscle forms the lower oesophageal sphincter?

A

Circular

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3
Q

What is the role of the lower oesophageal sphincter?

A

Prevents reflux of stomach contents

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4
Q

What is the role of the oblique muscle of the stomach and where is it?

A

Spirals around the stomach, providing a twisting movement

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5
Q

What three muscle layers are present in the walls of the stomach?

A

Longitudinal
Circular
Oblique

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6
Q

What is the pyloric sphincter?

A

Thickening of the circular muscle which controls the outflow f the stomach

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7
Q

How many units is the stomach made of?

A

2
1 = funds and body
2 = pylorus region

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8
Q

What are the 4 parts of the pyloric region of the stomach?

A

pyloric antrum (entrance)
pylorus
pyloric canal
pyloric sphincter

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9
Q

Is the lower oesophageal sphincter anatomical or physiological?

A

Physiological

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10
Q

Is the pyloric sphincter anatomical or physiological?

A

Anatomical

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11
Q

What is the role of the LES and cardia of the stomach?

A

Produces bicarb and mucus

Stops acid reflux into oesophagus

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12
Q

What is the role of the funds and body?

A

Modest motility - produces some persistalsis to move food down gradually but not too much
Can relax and act as a reservoir

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13
Q

What is the role of the antrum and pylorus?

A

Forceful peristalsis

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14
Q

Where in the stomach are HCO3- and mucus released?

A 
LES
Cardia
Fundus
Body
Anturm
Pylorus
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15
Q

Where in the stomach are intrinsic factor, H+, lipase and pepsinogens released?

A

Fundus and body

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16
Q

What are pepsinogens and where are they released?

A

Released by the fundus and cardia

Converted into pepsin by gastric acid, which breaks down proteins

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17
Q

What are pepsinogens and where are they released?

A

Released by the fundus and cardia

Converted into pepsin by gastric acid, which breaks down proteins

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18
Q

Which innervation allows the stomach to relax?

A

Parasympathetic - vagus

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19
Q

What reflex is required for accommodation of food in the stomach?
How does this work?

A

vago-vagal reflex
Stretch receptors signal via the vagus to say that the stomach is full, descending signals from the vagus act on the enteric nervous system to relax and dilate the funds and body

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20
Q

How much food can be stored in the stomach?

A

1 litre

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21
Q

What is a vagotomy?

A

Surgery were some branches of the vagus are cut to reduce the rate of gastric secretion - pressure rises more quickly so feel fuller quicker

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22
Q

What are the three phases across the antrum?

A

Propulsion
Emptying
Retropulsion

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23
Q

What are the largest particles that can pass into the duodenum?

A

1-2mm

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24
Q

What hormones are secreted by the duodenum to decrease gastric motility and emptying?
Why is emptying slowed?

A

CCK
Secretin
GIP

slowed to give the duodenum time to secrete suitable enzymes

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25
Q

What are gastric pits?

A

Indentations in the stomach which denote entrances to the tubular shaped gastric glands. Mucus cells are present in here, which also secrete HCO3-

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26
Q

What two types of cells are present in the body/fundus of the stomach?

A 
Parietal cells (oxyntic cells) - secrete acid (HCl) and intrinsic factor
Chief cells (peptic cells) - secrete pepsinogen
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27
Q

What cells are present in the antral region?

A

G cells - secrete gastrin into blood stream, found in antral/pyloric glands

28
Q

Where are chief cells (peptic cells) and parietal cells (oxyntic cells) found?

A

In the body/fundus

29
Q

Where are G cells found and what do they produce?

A

Gastrin

30
Q

What do oxyntic (parietal) cells produce?

A

Acid (Hcl) and intrinsic factor

31
Q

What do chief cells (peptic cells) secrete?

A

pepsinogen

32
Q

Which form of gastrin is secreted from the antrum?

A

G17

33
Q

Which form of gastrin is secreted from the duodenum?

A

G34

34
Q

What peptide hormone can gastrin share a receptor with? Why?

A

CCK (choleycystokinin, simulates digestion of fat and protein)
They share the same last 5 amino acids

35
Q

What is gastrin receptor also called?

A

CCK-B receptor

36
Q

What stimulates the release of gastrin?

A

Proteins/amino acids in the gut lumen

Parasympathetic input in response to gastric stretch

37
Q

What inhibits the release of gastrin?

A

Lumenal acid (H+) - negative feedback

38
Q

What is somatostatin?

A

A counter hormone to gastrin - acts on G cells to inhibit the release of gastrin, and also inhibits the release of CCK and secretin

39
Q

What are gastrin’s 2 main actions on the stomach?

A

Stimulate acid secretion

Promote mucosal growth

40
Q

Where is somatostatin released?

A

D cells in stomach, duodenum and pancreas

41
Q

How is somatostatin released?

A

Paracrine - into interstitium to act on adjacent cells

42
Q

What stimulates the release of somatostatin?

A

Lumenal H+

Acetylcholine (parasympathetic innervation)

43
Q

What is the structure of parietal (oxyntic) cells?

A

Infolded apical membranes
tubulovesicles with protein pumps in the cytoplasm secrete acid - become invaginated in the apical membrane when stimulated by gastrin to secrete acid. This increases the SA.
Lots of mitochondria so very metabolically active.

44
Q

What is the role of parietal cells?

A

Acid secretion

45
Q

What stimulates acid secretion from parietal cells?

A

Gastrin

ACh

46
Q

What inhibits acid secretion from parietal cells?

A

somatostatin

47
Q

What protects the epithelium of the stomach?

A

bicarbonate and mucus

48
Q

How do parietal cells secrete acid?

A

H+/K+ ATPase pump

K+ flow into cell and H+ leave. H+ enter the stomach and HCO3- is kicked out into the circulation. This creates an ALKALINE TIDE - blood pH starts to rise.
bit confused - research that

49
Q

When is the alkaline tide caused in the stomach balanced out?

A

Later in the gut, particularly in the colon where bicarb is secreted and there is an acid tide

50
Q

What indirectly mediates acid secretion by parietal (oxyntic) cells?

A

Histamine

51
Q

What is the target of proton pump inhibitors to manage ulcer disease etc?

A

Proton pump in parietal (oxyntic) cells in stomach to reduce HCl secretion

52
Q

How do NSAIDs increase acid production? What are the dangers of this?

A

NSAIDs block prostaglandin production
Prostaglandins inhibit acid production
NSAIDs therefore increase acid production, and may cause gastric ulcers

53
Q

Why do epithelial cells on the stomach surface produce bicarb and mucus? How does H pylori affect this?

A

Acid would dame these cells
Mucus layer protects them, and bicarb is secreted into mucus to keep pH around 7

H.Pylori gets into mucus and allows acid to damage epithelial cells

54
Q

Where is intrinsic factor released from? Does it have an effect on the stomach?

A

Parietal (oxyntic) cells

Not much affect in the stomach - binds to vit B12 in small intestine to act as a tag for cobalamin uptake

55
Q

What is the role of chief cells in the stomach?

A

Secrete pepsinogen

56
Q

What stimulates and chief cells?

A

Gastrin, Seprotin
Vagus
H+

57
Q

What are pepsins?

A

Proteases secreted from chief and mucus cells in response to ACh and H+ as pepsinogens (not active form).
Cleaved spontaneously at low pH

58
Q

Why aren’t pepsins secreted from chief cells as active form?

A

So they don’t damage the stomach cells that secrete them

59
Q

What are endoproteases?

A

will only cut long peptide chains, and will cut within the chain not at the end
broad specificity

60
Q

What is the role of gastric lipase?

A

Initial breakdown of fatty acids
Cleaves off the outer triglycerides
Works with lingual lipase

pH optimum 4

61
Q

What is the role of ptyalin a-amylase?

A

Initial digestion of polysaccharides in the fundus and body (where theres not much acid)

pH optimum 7

62
Q

Where is vomiting controlled?

A

Centrally in the brain stem

area postrema

63
Q

What is retrograde peristalsis?

A

Gut moves food backwards during vomiting

peristaltic waves are also much larger than usual

64
Q

Why do people retch when being sick?

A

involuntary contractions of the diaphragm and abdominal wall muscles to force material back up through the oesophagus

65
Q

What can happen temporarily to the position of the stomach during vomiting?

A

Displacement of the cardia into the thorax

gi (10 decks)

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