S5) Function and Pathology of the Stomach Flashcards
What do epithelial cells do in the stomach?
Epithelial cells cover the surface and extend into pits/glands
Identify 4 epithelial cells in the stomach
- Mucous cells
- Parietal cells
- Chief cells
- G cells
Identify the muscle layers in the stomach
- Circular
- Longitudinal
- Oblique
What is the effect of stomach muscle contractions?
- Mix/grind contents
- Move contents along
What is the function of the upper stomach?
The upper stomach has sustained contractions (tonic) to create basal tone
The lower stomach is more muscular.
Describe its function
The lower stomach has strong peristalsis which mixes stomach contents
Describe how contractions occur in the stomach
- Contractions are coordinated
- Contractions occur every 20 seconds
- Contraction are proximal to distal
What is receptive relaxation?
Receptive relaxation is the vagally mediated relaxation of orad stomach
What is the purpose of receptive relaxation?
- 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
Identify 3 functions of the acidic conditions of the stomach
- Helps unravel proteins
- Activates proteases: pepsinogen → pepsin
- Disinfects stomach contents
Identify 4 substances which are secreted by the stomach
- HCl
- Intrinsic factor
- Mucus/HCO3-
- Pepsinogen (pepsin)
Identify the substances secreted from the following cells:
- Parietal cell
- G cell
- Enterochromaffin like cell
- Parietal cell: HCl & intrinsic factor
- G cell: gastrin
- Enterochromaffin like cell (ECL): histamine
Identify the substances secreted from the following cells:
- Chief cell
- D cells
- Mucous cells
- Chief cell: pepsinogen
- D cells: somatostatin
- Mucous cells: mucus
Identify the substances secreted from the following regions in the stomach:
- Cardia
- Fundus/body
- Pylorus
- Cardia: predominantly mucus secretion
- Fundus/body: mucus, HCL, pepsinogen
- Pylorus: gastrin, somatostatin
Identify the 3 substances which stimulate HCl production and state their origins
- Gastrin from G cell
- Histamine from ECL cells
- Acetylcholine from vagus nerve
Where are G cells located?
G cells located in antrum
Identify the 2 factors which stimulate Gastrin secretion
- Peptides/AA in stomach lumen
- Vagal stimulation:
I. Acetylcholine
II. Gastrin-releasing peptide (GRP)
When food leaves the stomach, the pH drops.
How can HCl production be inhibted?
- Low pH stimulates D cells which release somatostatin
- Somatostatin inhibits G cells and ECL cells
- Stomach distension reduces due to reduced vagal activity
Identify the 3 phases of digestion
- Cephalic
- Gastric
- Intestinal
How much HCl is produced in the cephalic phase?
30% of total HCl
Outline the parasympathetic stimuli in the cephalic phase of digestion
- Smelling, tasting, chewing, swallowing
- Direct stimulation of parietal cells by vagus nerve
- Vagus nerve releases GRP which stimulates of G cells
How much HCl is produced in the gastric phase of digestion?
60% of total HCl
State 4 events which occur in the gastric phase of digestion
- 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)
What is the role of the enteric nervous system in the gastric phase of digestion?
ENS and gastrin causes strong smooth muscle contractions
How much HCl is produced in the intestinal phase of digestion?
10% of total HCl production
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
Which substances are released to protect the stomach lining?
- Mucus
- HCO3-
Where are mucus and hydrogen carbonate secreted from in the stomach?
- Surface mucus cells
- Neck cells in gastric glands
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
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
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
Up to 40% of adults suffer from dyspepsia per year.
What is dyspepsia?
Dyspepsia is pain/discomfort in the upper abdomen
Identify 6 common gastric disorders
- Gastro-oesophageal reflux disease (GORD)
- Gastritis
- Peptic ulcer disease
- Zollinger-Ellison disease
- Stress ulcers
- Stomach cancer
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
Identify 4 symptoms of GORD
- Heartburn
- Cough
- Sore throat
- Dysphagia
Identify 4 causes of GORD
- LOS problems
- Delayed gastric emptying (raised intra-gastric pressure)
- Hiatus hernia
- Obesity
Identify 3 compound problems which can arise from GORD?
- Oesophagitis
- Strictures
- Barrett’s oesophagus
Identify 3 types of treatment for GORD
- Lifestyle modifications
- Pharmacological
- Surgery (rare)
Identify 3 types of pharmacological treatments for GORD
- Antacids
- H2 antagonists
- PPIs
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)
What is gastritis?
Gastritis is a condition involving the inflammation of the stomach lining
What are the 2 types of gastritis which can occur in the body?
- Acute
- Chronic
Acute gastritis is an acute mucosal inflammatory process.
Identify 4 of its causes
- Heavy use of NSAIDS
- Lots of alcohol
- Chemotherapy
- Bile reflux
Identify the possible symptoms which may arise from acute gastritis
- Either: asymptomatic
- Or: pain, nausea, vomiting and occasional bleeding
What are the 2 types of chronic gastritis which can occur in the body?
- Autoimmune
- Bacterial
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
Identify a complication of chronic autoimmune gastritis
Autoimmune gastritis can lead to pernicious anaemia
Identify the possible symptoms which may arise from chronic bacterial gastritis
- Either: asymptomatic
- Or: pain, nausea, vomiting and occasional bleeding
In chronic bacterial gastritis, symptoms may develop due to complications.
Identify 3 of its complications
- Peptic ulcers
- Adenocarcinoma
- MALT lymphoma
Identify the symptoms of chronic autoimmune gastritis
- Symptoms of anaemia
- Glossitis
- Anorexia
- Neurological symptoms
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
Identify 2 common locations of peptic ulcers
- Most common in first part of duodenum
- Commonly affects lesser curve of stomach
Peptic ulcer disease is caused by mucosal injury.
Identify 3 factors which may cause/contribute to this injury
- Stomach acid
- H. pylori
- NSAIDS
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)
Identify 3 serious symptoms of peptic ulcer disease
- Bleeding/anaemia
- Satiety (early)
- Weight loss
What is Zollinger-Ellison syndrome?
Zollinger-Ellison syndrome is a condition when 1/more gastrin-secreting tumors (gastrinoma) form in your pancreas and duodenum
What is stomach cancer?
Stomach cancer is a condition which involves tumour formation in the stomach lining
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)
Identify 3 ways of treating gastric pathologies
- Eradicate H-pylori (PPI+ Clarithromycin + Amoxicillin)
- Stop NSAIDS
- PPIs
Identify 2 pharmacological interventions for gastritis and provide examples for each
- H2 blockers e.g. cimetidine, ranitidine
- Proton pump inhibitors e.g. omeprazole
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
How does H.pylori spread?
Oral to oral/faecal to oral
Identify 3 of H.pylori’s destructive functions
- Releases enzymes (urease) causing direct epithelial injury
- Degrades mucus layer
- Promotes inflammatory response (self injury)
State how the symptoms of H.pylori vary according to location
- Antrum: duodenal ulceration
- Antrum and body: asymptomatic
- Body: leads to cancer
Identify 5 causes of stress ulcerations
- Severe burns
- Raised intracranial pressure
- Sepsis
- Severe trauma
- Multiple organ failure
