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GI > 8. Functions Of The Stomach > Flashcards

8. Functions Of The Stomach Flashcards

1
Q

What is the function of the smooth muscle in the upper stomach?

A

Has sustained contractions.

Creates basal tone.

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2
Q

What is the function of the smooth muscle in the lower stomach?

A

Strong peristalsis mixes the stomach contents in coordinated movements every 20 seconds, proximal to distal.

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3
Q

What is the purpose of the stomach being larger proximally and smaller distally?

A

Accelerates contents, lumps are left behind.

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4
Q

How many times a minute is liquid chyme injected into the duodenum?

A

3 times a minute.

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5
Q

What is receptive relaxation?

A

Vagally mediated relaxation of the orad stomach.

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6
Q

What is the purpose of receptive relaxation of the stomach?

A

Allows food to enter the stomach without raising intra-gastric pressure too much.
Prevents reflex of stomach contents during swallowing.

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7
Q

Give 3 purposes for having acidic conditions in the stomach

A

Helps unravel proteins.
Activated proteases (pesinogen to pepsin).
Disinfects stomach contents.

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8
Q

What do the parietal cells in the stomach secrete?

A

HCL and intrinsic factor.

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9
Q

What do G cells in the stomach secrete?

A

Gastrin.

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10
Q

What do enterochromaffin like cells (ECL) in the stomach secrete?

A

Histamine.

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11
Q

What do chief cells in the stomach secrete?

A

Pepsinogen.

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12
Q

What do D cells in the stomach secrete?

A

Somatostatin.

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13
Q

What do mucous cells in the stomach secrete?

A

Mucus.

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14
Q

What do cells found in the cardia of the stomach predominantly secrete?

A

Predominantly mucus secretion.

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15
Q

What do cells in the fundus/body of the stomach predominantly secrete?

A

Mucus, HCL, pepsinogen.

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16
Q

What do cells in the pyloric us of the stomach predominantly secrete?

A

Gastrin and somatostatin.

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17
Q

What stimulates parietal cells to secrete HCL?

A

Gastrin - from G cells.
Histamine from enterocyte-chromaffin like cells.
ACh from the vagus nerve.

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18
Q

Where in the stomach are G cells located?

A

Antrum - lower stomach.

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19
Q

What stimulates G cells to secrete gastrin?

A

Peptides/amino acids in the stomach lumen.
Vagal stimulation releasing acetylcholine and gastrin-releasing peptide (this is to prepare the stomach to receive food).

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20
Q

How are G cells and therefore HCL production inhibited?

A

When food leaves the stomach the pH drops (more acidic). The low pH activated D cells, which release somatostatin. Somatostatin inhibits G cells.
Stomach distension reduced when food leaves the stomach, reducing vagal activity.

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21
Q

What are the 3 stages of digestion? What percentage of HCL production does each account for?

A

Cephalic - 30%.
Gastric - 60%.
Intestinal - 10%.

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22
Q

What happens in the cephalic phase of digestion?

A

Parasympathetic stimuli:
Setting, tasting, chewing, swallowing.
Direct stimulation of the parietal cell by the vagus nerve.
Stimulation of G cells by the vagus nerve.
Anticipating food increases gastric motility slightly.

23
Q

What happens in the gastric phase of digestion?

A

Distension of the stomach stimulates the vagus nerve which then stimulates parietal cells and G cells.
Presence of amino acids and small peptides stimulates G cells.
Food acts as a buffer in the stomach removing inhibition on G cells.

24
Q

What happens in the intestinal phase of digestion?

A

Chyme initially stimulates gastrin section as the partially digested proteins are detected in the duodenum.
Then there is inhibition of G cells by the presence of lipids activating the enterogastric reflex, reducing vagal stimulation, and chyme stimulates CCK and secretin, which stimulate the pancreas and gallbladder, and suppress gastric secretion and motility.

25
Q

What two things cause strong muscle contractions in the stomach?

A

The enteric nervous system.

Gastrin.

26
Q

What protects the stomach from being digested?

A

Mucus and HCO3- forms with alkaline viscous layer that adheres to epithelium.
High turnover of epithelial cells keeps epithelia in tact.
Prostaglandins maintain mucosal blood flow supplying epithelium with nutrients.

27
Q

How does alcohol breach the stomach defences?

A

Dissolves the mucus layer.

28
Q

How does helicobacter pylori breach the stomach defences?

A

Causes chronic active gastritis, which affects the high turnover of epithelial cells.

29
Q

How do NSAIDS breach the stomach defences?

A

Inhibit prostaglandin, preventing inhibition of HCl production.

30
Q

What is gastrointestinal-oesophageal reflux disease?

A

Reflux of the stomach contents in to the oesophagus.

31
Q

Give 3 symptoms of gastrointestinal-oesophageal reflux disease

A

Heartburn.
Cough.
Sore throat.
Dysphagia.

32
Q

Give 3 causes of gastrointestinal-oesophageal reflux disease

A

Lower oesophageal problems.
Delayed gastric emptying (leading to raised intra-gastric pressure).
Hiatus hernia.
Obesity.

33
Q

What other conditions can gastrointestinal-oesophageal reflux lead to?

A

Oesophagitis.
Strictures.
Barrett’s oesophagus.

34
Q

What is Barrett’s oesophagus? What does it lead to an increased risk of?

A

Metaplasia of squamous epithelium to columnar.

Increased risk of developing adenocarcinoma.

35
Q

What are the main treatment options for gastrointestinal-oesophageal reflux?

A

Lifestyle modifications eg losing weight to reduce intra-abdominal pressure.
Pharmacological eh antacids, H2 antagonists, PPIs.
Surgery (rare).

36
Q

What is acute gastritis?

A

An acute mucosal inflammatory process.

37
Q

Give 3 causes of acute gastritis

A

Heavy use of NSAIDS.
Lots of alcohol.
Chemotherapy.
Bile reflux.

38
Q

Give 3 symptoms of acute gastritis

A 
Asymptomatic.
Pain.
Nausea.
Vomiting
Occasionally bleeding (can be fatal).
39
Q

What can cause chronic gastritis?

A

Bacterial - H-pylori infection.
Autoimmune - antibodies to gastric parietal cells can lead to pernicious anaemia.
Chemical - chronic alcohol abuse, NSAIDS, reflux of bile.

40
Q

What are the symptoms of chronic gastritis caused by helicobacter-pylori?

A

Asymptomatic.
Pain, nausea, vomiting.
Symptoms may develop due to complications eg peptic ulcers, adenocarcinoma, MALT lymphoma.

41
Q

What are the symptoms of chronic gastritis caused by autoimmunity?

A

Symptoms of anaemia eg fatigue, pale skin, shortness of breath, difficulty concentrating.
Glossitis.
Anorexia.
Neurological symptoms.

42
Q

What is peptic ulcer disease?

A

Defects in the gastric/duodenal mucosa, extending through the muscularis mucosa.

43
Q

Where does peptic ulcer disease most commonly affect?

A

First part of duodenum and lesser curve of stomach.

44
Q

Give 3 causes of peptic ulcer disease

A

Mucosal injury by:
Stomach acid.
H-pylori.
NSAIDs.
Smoking (only contributes to relapse of ulcer disease).
Massive physiological stress eg in burns, raised intracranial pressure, sepsis, severe trauma, multiple organ failure.

45
Q

Give 3 symptoms of peptic ulcer disease

A

Epigastric pain (sometimes back pain), which is burning/gnawing, follows meal times and often at night (especially with duodenal ulcers).
Bleeding/anaemia.
Early satiety.
Weight loss.

46
Q

What procedures/tests can be used to diagnose gastric pathology?

A 
Upper GI endoscopy with biopsies.
Urease breath test (to detect H-pylori).
Erect test X-ray - show perforation.
Blood test - for anaemia.
Check for melena.
47
Q

How can gastric pathology (eg gastritis, ulcers) be treated?

A

Eradicate H-pylori - triple therapy (PPI, clarithromycin, amoxicillin).
Stop NSAIS.
Endoscopy for bleeding ulcers.
Follow up for treated gastric ulcers.
PPIs eg omeprazole - prevent HCL release.
H2 (histamine) blockers eg ranitidine - prevent HCL release.

48
Q

How is helicobacter-pylori spread?

A

Oral to oral or faecal to oral.

49
Q

Is helicobacter-pylori gram positive or negative?

A

Gram negative.

50
Q

Give 3 ways that helicobacter-pylori damage the GI tract?

A

Produces urease which converts urea to ammonia, increasing local pH but ammonia is toxic to epithelia.
Has a flagellum so good motility allowing it to live in the mucus layer (possibly degrading the mucus layer) or adhere to the gastric epithelia.
Releases cytotoxins which cause direct epithelial injury.
Promotes inflammatory response.

51
Q

What type of ulceration tends to be caused if there is a H-pylori colonisation in the antrum of the stomach?

A

Duodenal ulceration.

52
Q

What type of ulceration tends to be caused if there is a H-pylori colonisation in both the body and antrum of the stomach?

A

Asymptomatic.

53
Q

What type of ulceration tends to be caused if there is a H-pylori colonisation in the body of the stomach?

A

Can lead to cancer.

GI (15 decks)

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