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Gastrointestinal Tract > 7) Functions of the Stomach > Flashcards

7) Functions of the Stomach Flashcards

1
Q

What are the basic functions of the stomach (4)?

A

Stores food
Disrupts food (contractions)
Continues digestion
Disinfects food

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2
Q

What is the first section of the stomach called?

A

Cardia, where oesophagus enters

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3
Q

What are the other sections of the stomach (top to bottom)?

A

Fundus, body, antrum, pylorus (+sphincter)

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4
Q

What is the change in epithelium at the cardia?

A

Transition of stratified squamous to columnar (secretion)

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5
Q

Describe the muscosa of the stomach:

A

In folds (rugae), to allow distension by flattening of these folds

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6
Q

What are gastric pits?

A

‘Little holes’ on stomach surface

These pits have gastric glands (specialised cells) at the bottom

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7
Q

What causes the movement of substances from the cardia to pylorus?

A

Upper stomach has basal tones created by sustained contractions which force flow down funnel shaped stomach

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8
Q

How many muscle layers does the stomach have?

A

3 - oblique, circular and outer longitudinal

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9
Q

What is receptive relaxation?

A

As food travels down oesophagus, vagus nerve triggers relaxation of orad stomach wall (flattening of rugae)

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10
Q

What does receptive relaxation stop?

A

Stops rises in intra-gastric pressure

Prevents reflux

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11
Q

What are the functions of stomach acid?

A

Helps unravel proteins - larger SA
Activates proteases - pepsin
Disinfection

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12
Q

What do parietal cells secrete?

A

HCl

Intrinsic factor

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13
Q

What do G cells secrete?

A

Gastrin

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14
Q

What do enterochromaffin like cells secrete?

A

Histamine

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15
Q

What do chief cells secrete?

A

Pepsinogen

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16
Q

What do D cells secrete?

A

Somatostatin

17
Q

What do mucous cells (surface + neck) secret?

A

Mucus

18
Q

What are the predominant secretions of the cardia?

A

Mucus

19
Q

What are the main secretions of the fundus and body?

A

Mucus, HCl, pepsinogen

20
Q

What are the main secretions of the pylorus?

A

Gastrin, somatostatin

21
Q

What stimulates secretion of stomach acid?

A

Gastrin, histamine and ACh

22
Q

What feature of the parietal cell allows increased acid secretion?

A

Invaginations on cell surface (canaliculi) increase SA for secretion

23
Q

What stimulates gastrin secretion?

A

Peptides/AAs in the stomach lumen

Vagus stimulation - ACh, gastrin releasing peptide

24
Q

What inhibits acid production?

A

Low stomach pH - food acts as buffer
Low pH also activates D cells –> somatostatin which inhibits G and ECL cells
Reduction in stomach distension reduces vagal activity

25
Q

Describe the formation of HCl:

A

Water split to OH- and H+
H+ and Cl- into stomach lumen to form HCl
Uses H+/K+ ATPase

26
Q

What happens to the OH- produced in HCl formation?

A

Combines with CO2 to form HCO3-

This moves into bloodstream, alkaline tide (HCO3-/Cl- antiporter)

27
Q

What are the 3 phases of digestion?

A

Cephalic
Gastric
Intestinal

28
Q

What occurs in the cephalic phase of digestion?

A

Vagus nerve stimulates parietal and G cells in response to smelling, tasting, chewing and swallowing
Increase in gastric motility
30% of HCl

29
Q

What occurs in the gastric phase of digestion?

A

Distension of stomach stimulates vagus (parietal and G cells)
Presence of AA/peptides stimulates G cells
Food acts as buffer so no inhibition of gastrin
Enteric NS and gastrin cause strong SM contractions

30
Q

What occurs in the intestinal phase of digestion?

A

Inhibition of G cells due to presence of lipids - enterogastric reflex, reduced vagal
Chyme stimulates CCK and secretin

31
Q

What defences does stomach have against acid?

A

Mucus and HCO3- - form thick alkaline viscous layer over epithelium
High turnover of epithelial cells
Prostaglandins maintain mucosal blood flow

32
Q

What can breach stomach defences?

A

Alcohol - dissolves mucus layer
Helicobacter pylori - inflamm of stomach lining
NSAIDS - inhibit prostaglandins

33
Q

What can breach of stomach defence lead to?

A

Gastritis
Ulceration
Reflux disease

34
Q

What pharmacological interventions can be used to reduce acid secretion?

A

H2 blockers - cimetidine

Proton pump inhibitors - omeprazole

35
Q

What slows gastric emptying?

A

Fat, low pH and hypertonicity in duodenum

Gastrointestinal Tract (11 decks)

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