E2. Biology of dyspepsia Flashcards
what are the symptoms of dyspepsia?
-upper abdominal pain or discomfort
-heartburn
-gastric reflux
-nausea
-vomiting
Problems are related to hydrochloric acid produced in the stomach (gastric acid).
Describe gastric ulcer
-Protective (epithelial) layer damaged
-underlying tissue (connective, muscle and nerve tissue) exposed
-bleeding can be caused by (acid) damage to blood vessels
Describe reflux (oesophagus):
limited protection against gastric acid; excess acid can cause tissue damage
Describe the stomach
Most acid-secreting cells (parietal cells) are localised in a specific region in the stomach (fundus).
Describe sphincters
Two sphincters prevent excess acid in the intestine and oesophagus-Compartmentalisation.
Describe the stomach epithelium
-The majority of the stomach is lined with simple epithelium: a single layer of epithelial cells
-These cells are called surface mucous cells, or foveolar cells
-Secrete a layer (mucus) that protects the lining of the stomach
How does the mucus protect against acid?
-Glycosylated proteins form a thick, gel-like layer on surface of cells
-HCO3¯ (bicarbonate) neutralises gastric acid
-Acid in the stomach does not easily mix with mucus
Describe how tight junctions protect against acid
Mucous surface cells are connected via tight junctions:
-Protein structures that restrict movement of ions and water between cells
-Prevents acid leaking through the epithelial layer
-Prevents damage to underlying tissue
Tight junctions divide the cell membrane in what two compartments?
-apical (“outside”; towards the lumen)
-basolateral (“inside”; facing the basement membrane)
ONE NOTE
Describe the stomach in gastro- oesophageal reflux disease (GORD)
-Simple columnar epithelium
-Mucous cells cover most of the internal surface
-adequate protection against gastric acid
ONE NOTE
Describe the oesophagus in gastro- oesophageal reflux disease (GORD)
-non-keratinised stratified squamous epithelium
-specialised Goblet cells secrete mucus
-less protection against gastric acid.
ONE NOTE
Gastric acid is secreted by?
parietal cells
where are parietal cells located?
gastric pits
function of acid?
-Conversion of pepsinogen to pepsin (enzyme that breaks down protein)
-Kills many types of bacteria
Describe structure of gastric pit
ONE NOTE
Acid secretion is stimulated by what extracellular signals?
-histamine
-acetylcholine
-gastrin (peptide hormone)
These signals can activate parietal cells by interacting with receptors localised on basolateral membrane
ONE NOTE
Describe secretion of HCl by parietal cells
-Uptake of CO2 by diffusion
-Hydration of CO2 by carbonic anhydrase enzyme
-H+ exported by the gastric proton pump
ONE NOTE
What kind of receptor is a H2 receptor?
G protein coupled receptor
Describe H2 receptor antagonists
-Prevent binding of the natural ligand histamine.
-The receptor cannot be activated by histamine.
Describe ion pumps
-Multiple subunits
-Gastric proton pump
a-subunit and B-subunit of transmembrane helices
-Other types of proton pumps: located in mitochondrial membrane
Describe gastric proton pump
Full Name: H+ K+
ATPase
Functions: Gastic acid secretion
Exchanges: 2H+/2K+
ONE NOTE
How do proton pump inhibitors reach their targets?
ONE NOTE
