Gastric motility and pancreatic function Flashcards
What is a peristaltic wave?
Its when smooth muscle tissue contracts in sequence to produce a peristaltic wave, which the bolus along the tract
How does a peristaltic wave travel?
It goes down the oesophagus down to the antrum
What is peristalsis?
It is involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but occasionally in other hollow tubes of the body, that occur in progressive wavelikecontractions
Gastric motility in the body of stomach
Thin muscle > weak contraction > no mixing
Gastric motility in antrum of stomach
Thick muscle > powerful contraction >
a) mixing
b) Contraction of pyloric sphincter > only small quantity of gastric content (chyme) entering duodenum > Further mixing as antral contents forced back towards body
What produces gastric peristaltic waves?
Peristaltic rhythm (3/min) generated by pacemaker cells (longitudinal muscle layer)
How do slow waves affect peristaltic waves?
Slow waves cause spontaneous depolarisation/repolarisation
Slow wave rhythm = basic electrical rhythm (BER)
How are slow waves conducted?
They are conducted through gap junctions along longitudinal muscle layer
Do depolarisations cause contractions?
No :(
What does gastrin do?
Stimulates gastric acid secretion and mucosal growth
How does gastrin affect contraction?
It increases contraction
How does fat/acid/amino acid/hypertonicity in duodenum affect motility?
It causes inhibition of motility
What is used to neutralise acid in the duodenum?
Bicarbonate (HCO3) secretion from Brunner’s gland duct cells (submucosal glands)
What does acid in duodenum trigger?
a) Long (vagal) & short (ENS) reflexes > HCO3 secretion
b) Release of secretin from S cells > HCO3 secretion
What does secretin do?
It causes HCO3 secretion from pancreas & liver
What does achieving acid neutralisation do to secretin release?
It inhibits secretin release (negative feedback control)
What are the 3 main parts of the pancreas?
Head (located within curvature of duodenum)
Body
Tail (extends to spleen)
What is the endocrine portion of the pancreas composed of?
Endocrine portion > pancreatic islets (islets of Langerhans)
What do pancreatic islet cells produce?
Insulin
Glucagon (control [bood glucose])
Somatostatin (controls secretion of insulin and glucagon)
What is the exocrine portion of the pancreas composed of?
Exocrine portion > acinar cells > lobules
What are lobules of the pancreas connected by?
Lobules connected by intercalated ducts > intralobular ducts > interloular ducts > main pancreatic duct > common bile duct > hepatopancreatic ampulla (Sphincter of Oddi) > duodenum
Also accessory pancreatic duct > duodenum
What is the sphincter of Oddi responsible for?
It controls delivery of pancreatic juice and bile into duodenum
What is another name for sphincter of Oddi?
Major duodenum papilla
What is the exocrine pancreas responsible for?
Digestive function of pancreas
