S5) Function and Pathology of the Stomach Flashcards
1
Q
What do epithelial cells do in the stomach?
A
Epithelial cells cover the surface and extend into pits/glands
2
Q
Identify 4 epithelial cells in the stomach
A
- Mucous cells
- Parietal cells
- Chief cells
- G cells
3
Q
Identify the muscle layers in the stomach
A
- Circular
- Longitudinal
- Oblique
4
Q
What is the effect of stomach muscle contractions?
A
- Mix/grind contents
- Move contents along
5
Q
What is the function of the upper stomach?
A
The upper stomach has sustained contractions (tonic) to create basal tone
6
Q
The lower stomach is more muscular.
Describe its function
A
The lower stomach has strong peristalsis which mixes stomach contents
7
Q
Describe how contractions occur in the stomach
A
- Contractions are coordinated
- Contractions occur every 20 seconds
- Contraction are proximal to distal
8
Q
What is receptive relaxation?
A
Receptive relaxation is the vagally mediated relaxation of orad stomach
9
Q
What is the purpose of receptive relaxation?
A
- Allows food to enter stomach without raising intra-gastric pressure too much
- Prevents reflux of stomach contents when swallowing
- Gastric mucosal folds (rugae) allow distension
10
Q
Identify 3 functions of the acidic conditions of the stomach
A
- Helps unravel proteins
- Activates proteases: pepsinogen → pepsin
- Disinfects stomach contents
11
Q
Identify 4 substances which are secreted by the stomach
A
- HCl
- Intrinsic factor
- Mucus/HCO3-
- Pepsinogen (pepsin)
12
Q
Identify the substances secreted from the following cells:
- Parietal cell
- G cell
- Enterochromaffin like cell
A
- Parietal cell: HCl & intrinsic factor
- G cell: gastrin
- Enterochromaffin like cell (ECL): histamine
13
Q
Identify the substances secreted from the following cells:
- Chief cell
- D cells
- Mucous cells
A
- Chief cell: pepsinogen
- D cells: somatostatin
- Mucous cells: mucus
14
Q
Identify the substances secreted from the following regions in the stomach:
- Cardia
- Fundus/body
- Pylorus
A
- Cardia: predominantly mucus secretion
- Fundus/body: mucus, HCL, pepsinogen
- Pylorus: gastrin, somatostatin
15
Q
Identify the 3 substances which stimulate HCl production and state their origins
A
- Gastrin from G cell
- Histamine from ECL cells
- Acetylcholine from vagus nerve
16
Q
Where are G cells located?
A
G cells located in antrum
17
Q
Identify the 2 factors which stimulate Gastrin secretion
A
- Peptides/AA in stomach lumen
- Vagal stimulation:
I. Acetylcholine
II. Gastrin-releasing peptide (GRP)
18
Q
When food leaves the stomach, the pH drops.
How can HCl production be inhibted?
A
- Low pH stimulates D cells which release somatostatin
- Somatostatin inhibits G cells and ECL cells
- Stomach distension reduces due to reduced vagal activity
19
Q
Identify the 3 phases of digestion
A
- Cephalic
- Gastric
- Intestinal
20
Q
How much HCl is produced in the cephalic phase?
A
30% of total HCl
21
Q
Outline the parasympathetic stimuli in the cephalic phase of digestion
A
- Smelling, tasting, chewing, swallowing
- Direct stimulation of parietal cells by vagus nerve
- Vagus nerve releases GRP which stimulates of G cells
22
Q
How much HCl is produced in the gastric phase of digestion?
A
60% of total HCl
23
Q
State 4 events which occur in the gastric phase of digestion
A
- Stomach distension stimulates vagus nerve
- Vagus nerve stimulates parietal cells and G cells
- Amino acids and small peptides stimulates G cells
- Presence of food acts removes inhibition on Gastrin production (buffer)
24
Q
What is the role of the enteric nervous system in the gastric phase of digestion?
A
ENS and gastrin causes strong smooth muscle contractions
25
How much HCl is produced in the intestinal phase of digestion?
10% of total HCl production
26
State the 4 events occurring in the intestinal phase of digestion
- Chyme **stimulates gastrin secretion** due to the detection of partially digested proteins by duodenum
- G cells are then inhibited
- **Enterogastric reflex** is activated by lipids which reduces **vagal stimulation**
- Chyme then stimulates **CCK** and **secretin**
27
Which substances are released to protect the stomach lining?
- Mucus
- HCO3-
28
Where are mucus and hydrogen carbonate secreted from in the stomach?
- Surface mucus cells
- Neck cells in gastric glands
29
What are the effects of mucus and hydrogen carbonate secretion in the stomach?
- Thick alkaline viscous layer is formed which adheres to epithelium
- Epithelial surface kept at higher pH
30
Apart from mucus/HCO3-, identify and describe 2 other stomach defences
- **High turnover of epithelial cells** to keep epithelia intact
- **Prostaglandins** to maintain mucosal blood flow and supply epithelium with nutrients
31
Identify 3 substances that breach the stomach defences and state their effects
- **Alcohol** – dissolves mucus layer
- **Helicobacter pylori** – causes chronic active gastritis
- **NSAIDS** – inhibits prostaglandins
32
Up to 40% of adults suffer from dyspepsia per year.
What is dyspepsia?
**Dyspepsia** is pain/discomfort in the upper abdomen
33
Identify 6 common gastric disorders
- Gastro-oesophageal reflux disease (GORD)
- Gastritis
- Peptic ulcer disease
- Zollinger-Ellison disease
- Stress ulcers
- Stomach cancer
34
What is GORD?
**Gastro-oesophageal reflux disease** (GORD) is a digestive disorder that affects the lower oesophageal sphincter and causes the reflux of stomach acid/contents into the oesophagus
35
Identify 4 symptoms of GORD
- Heartburn
- Cough
- Sore throat
- Dysphagia
36
Identify 4 causes of GORD
- LOS problems
- Delayed gastric emptying (raised intra-gastric pressure)
- Hiatus hernia
- Obesity
37
Identify 3 compound problems which can arise from GORD?
- Oesophagitis
- Strictures
- Barrett’s oesophagus
38
Identify 3 types of treatment for GORD
- Lifestyle modifications
- Pharmacological
- Surgery (rare)
39
Identify 3 types of pharmacological treatments for GORD
- Antacids
- H2 antagonists
- PPIs
40
What is Barrett's Oesophagus?
- **Barrett’s oesophagus** is the metaplasia of squamous epithelium to columnar
- It increases the risk of developing **adenocarcinoma** (30-40x)
41
What is gastritis?
**Gastritis** is a condition involving the inflammation of the stomach lining
42
What are the 2 types of gastritis which can occur in the body?
- Acute
- Chronic
43
Acute gastritis is an acute mucosal inflammatory process.
Identify 4 of its causes
- Heavy use of NSAIDS
- Lots of alcohol
- Chemotherapy
- Bile reflux
44
Identify the possible symptoms which may arise from acute gastritis
- Either: asymptomatic
- Or: pain, nausea, vomiting and occasional bleeding
45
What are the 2 types of chronic gastritis which can occur in the body?
- Autoimmune
- Bacterial
46
Compare and contrast the causes of chronic autoimmune and bacterial gastritis
- **Bacterial Gastritis** – caused by H. pylori infection (commonly)
- **Autoimmune** **Gastritis** – caused by antibodies to gastric parietal cells
47
Identify a complication of chronic autoimmune gastritis
Autoimmune gastritis can lead to **pernicious anaemia**
48
Identify the possible symptoms which may arise from chronic bacterial gastritis
- Either: asymptomatic
- Or: pain, nausea, vomiting and occasional bleeding
49
In chronic bacterial gastritis, symptoms may develop due to complications.
Identify 3 of its complications
- Peptic ulcers
- Adenocarcinoma
- MALT lymphoma
50
Identify the symptoms of chronic autoimmune gastritis
- Symptoms of anaemia
- Glossitis
- Anorexia
- Neurological symptoms
51
What is peptic ulcer disease?
**Peptic ulcer disease** is a condition which occurs when ulcers form and extend into the muscularis mucosae of the stomach due to defects in the gastric/duodenal mucosa
52
Identify 2 common locations of peptic ulcers
- Most common in first part of duodenum
- Commonly affects lesser curve of stomach
53
Peptic ulcer disease is caused by mucosal injury.
Identify 3 factors which may cause/contribute to this injury
- Stomach acid
- H. pylori
- NSAIDS
54
A major symptom of peptic ulcer disease is epigastric pain.
Describe the features of this pain
- Burning/gnawing
- Follows meal times
- Often at night (especially DU)
55
Identify 3 serious symptoms of peptic ulcer disease
- Bleeding/anaemia
- Satiety (early)
- Weight loss
56
What is Zollinger-Ellison syndrome?
**Zollinger-Ellison syndrome** is a condition when 1/more gastrin-secreting tumors (gastrinoma) form in your pancreas and duodenum
57
What is stomach cancer?
**Stomach cancer** is a condition which involves tumour formation in the stomach lining
58
Identify 4 different means of diagnosing gastric pathology
- Upper GI endoscopy (biopsies/H-pylori)
- Urease breath test
- Erect chest X-ray (perforation)
- Blood test (anaemia)
59
Identify 3 ways of treating gastric pathologies
- Eradicate H-pylori (PPI+ Clarithromycin + Amoxicillin)
- Stop NSAIDS
- PPIs
60
Identify 2 pharmacological interventions for gastritis and provide examples for each
- H2 blockers *e.g. cimetidine, ranitidine*
- Proton pump inhibitors *e.g. omeprazole*
61
Describe the structure, function and location of Helicobacter pylori
- **Structure**: helix shaped, gram negative, flagellum
- **Function**: produces urease, converts urea to ammonium, increases local pH
- **Location**: mucus layer/adheres to gastric epithelia
62
How does H.pylori spread?
Oral to oral/faecal to oral
63
Identify 3 of H.pylori's destructive functions
- Releases enzymes (urease) causing direct epithelial injury
- Degrades mucus layer
- Promotes inflammatory response (self injury)
64
State how the symptoms of H.pylori vary according to location
- **Antrum**: duodenal ulceration
- **Antrum and body**: asymptomatic
- **Body**: leads to cancer
65
Identify 5 causes of stress ulcerations
- Severe burns
- Raised intracranial pressure
- Sepsis
- Severe trauma
- Multiple organ failure
