how would you describe the musculature of the oesophagus?
striated. the remainder is smooth and organised as outer longitudinal and inner circular layers
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what innervates the oesophagus?
vagus nerve - supplies the muscle directly. myenteric and sub mucous plexus supply the muscle indirectly.
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what triggers closure of the upper oesophageal sphincter?
swallowing centre (pons and medulla) and a primary peristaltic wave (via vagus)
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what I peristalsis co ordinated by?
enteric nervous system
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what does the lower oesophagus sphincter do to prevent reflux?
opens within 2-3 seconds of the initiation of a swallow (closes after the passage of bolus)
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what are the two types of mechanical activity of the stomach
orad stomach (fundus and proximal body) – tonic, i.e. maintained caudad stomach (distal body and antrum) – phasic, i.e. intermittent
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what is the orad region
relaxation driven by vagus occurs during a swallow (simultaneous with the opening of the lower oesophageal sphincter) permitting storage of ingested material no slow wave activity tonic contractions-weak due to relatively thin musculature
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what is the caudad region
driven by suprathreshold slow waves progress from midstomach to gastroduodenal junction (the antral wave) propelling contents towards pylorus through which a very small volume of chyme flows into the duodenum
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what governs stomach emptying
gastric and duodenal factors
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what are gastric factors
Rate of emptying proportional to volume of chyme in stomach. Distension increases motility due to: stretch of smooth muscle stimulation of intrinsic nerve plexuses increased vagus nerve activity and gastrin release
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what are duodenal factors? how does the duodenum delay emptying ?
Neuronal response: the enterogastric reflex – decreases antral activity by signals from intrinsic nerve plexuses and the ANS. Hormonal response – release of enterogastrones [e.g cholecystokinin CCK)] from duodenum inhibits stomach contraction
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what stimuli within the duodenum drive the neuronal and hormone response?
fat, acid, hypertonicity and distention
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how is mucosa of the stomach classes as?
the oxyntic gland area (proximal stomach including the fundus and body) the pylorlic gland area (distal stomach, designated the antrum)
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what is gastric mucosa composed of?
a surface lining the stomach pits, invaginations of the surface glands, at the base of the pits responsible for several secretions
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what are the functions of the gastric secretions? oxyntic mucosa
HCL, pepsinogen, mucus, histamine, intrinsic factor and gastroferrin
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what are the functions of pyloric gland area?
gastrin, somatostatin and mucus
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what are the three phases of gastric acid secretion?
cephalic, gastric and intestinal phase
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what is the cephalic phase?
Cephalic phase (‘in the head’) – before food reaches the stomach preparing it stomach to receive food driven directly and indirectly by the CNS and vagus nerves (CN X)
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in the cephalic phase- what does the enteric neurones do?
release ACh directly activating parietal cells (neurotransmitter action) via release of GRP causes release of gastrin from G cells in to systemic circulation that activates parietal cells (endocrine action) via release of histamine from ECL cells th
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drugs that reduce acid secretion are used in treatment of?
gastro oesophageal reflux diseases and acid hyper secretion
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what are some of the mechanisms of anti secretory activity?
irreversible inhibition of the proton-pump (H+/K+ ATPase. competitive antagonism of histamine H2 receptors. competitive antagonism of muscarinic M1 and M3 ACh receptors (mostly obsolete. antagonism of gastrin (CCK2) receptors (not utilized clinically
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give some features of the PPIs like omeprazole
inhibit the active (i.e. membrane inserted) H+/K+-dependent ATPase (proton-pump) . basic prodrugs that are inactive at neutral pH, but which change conformation in a strongly acidic environment. absorbed from the GI tract and delivered via the system
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what does omeprazole do?
inhibit acid secretion.
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what are histamine H2 receptor antagonists?
act as competitive (reversible) antagonists of H2 receptors.block the histamine-mediated component of acid secretion and reduce secretion evoked by gastrin and ACh. effective against basal and stimulated gastric acid production
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give two examples of mucosal strengtheners?
Sucralfate – a complex of aluminium hydroxide and sulphated sucrose and Bismuth chealate
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Other cards in this set
Card 2
Front
what kind of epithelium lines the oesophagus?
Back
stratified squamous
Card 3
Front
how would you describe the musculature of the oesophagus?
Back
Card 4
Front
what innervates the oesophagus?
Back
Card 5
Front
what triggers closure of the upper oesophageal sphincter?
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