Gastric motility and pancreatic function Flashcards
What sort of motility is there in the body of the stomach?
Thin muscles cause weak contractions
What sort of motility is there in the antrum of the stomach?
Thick muscle causes a powerful contraction and mixing of the gastric contents
Where is the pyloric sphincter?
Entrance to duodenum
What is the role of the pyloric sphincter?
Only a small amount of content can enter the duodenum
Further mixing as astral contents forced back
What is peristaltic rhythm?
3 waves per min
What is peristaltic rhythm created by?
Pacemaker cells in the longitudinal muscle
How is peristaltic rhythm created?
Spontaneous depolarisation of longitudinal muscle pacemakers
Conducted through gap junctions in longitudinal muscle
Further depolarisation causes it to reach threshold and induce action potentials, causing contraction
What determines the strength of peristaltic contraction?
The number of action potentials per wave
What is the neural and hormonal control of peristalsis?
Gastrin increases contraction
Distension of stomach wall causing stimulation of vagus nerve or ENS increases contraction
Fat/acid/amino acid/hypertonicity in duodenum causes inhibition of motility
How is acid neutralised in the duodenum?
Bicarbonate
What secretes bicarbonate in the duodenum?
Brunner’s gland duct cells
What controls duodenal bicarbonate secretion?
Acid in the duodenum
What are the methods by which bicarb secretion in the duodenum is controlled?
Vagal and ENS reflexes cause bicarbonate secretion
Release of secretin causes bicarb secretion from pancreas and liver
What inhibits secretin release?
Neutralisation of acid
What are the 3 parts of the pancreas?
Head
Body
Tail
Where is the head of the pancreas located?
Curvature of duodenum
Where is the tail of the pancreas?
Extending to spleen
What s present in the endocrine portion of the pancreas?
Pancreatic islets
What do pancreatic islets produce?
Insulin, glucagon and somatostatin
What is somatostatin?
Controls secretion of both insulin and glucagon
What is in the exocrine portion of the pancreas?
Acinar cells that form lobules connected by intercalated ducts
What do intercalated ducts form?
Intercalated ducts feed into intralobular ducts which form the main pancreatic duct –> common bile duct –> sphincter of Oddi–> duodenum
What is the accessory duct of the pancreas?
Extra duct feeding into duodenum that can open if other ducts are blocked
What is the exocrine pancreas responsible for?
Digestive function of pancreas
What does the exocrine pancreas secrete?
Bicarbonate by duct cells
Digestive enzymes by acing cells
What is a zymogen?
Inactive enzyme precursor
What do acing cells contain?
Digestive enzymes stored a zymogen granules
What does storage of enzymes as zymogens do?
Prevent auto digestion of pancreas
How are pancreatic enzymes converted out of the zymogen form?
Membrane bound enterokinase converts trypsinogen to trypsin which converts all other zymogens to active forms
What are the categories of pancreatic enzymes?
Proteases Nucleases Elastases Phospholipases alpha amylase
What do proteases to?
Cleave peptide bonds
What do nucleases do?
Hydrolyse DNA/RNA
What do elastase do?
Digest collagen
What do phospholipase do?
Convert phospholipids to fatty acids
What do lipase do?
Breakdown triacylglycerol to monoglyceride and fatty acids
What does alpha amylase do?
Converts starch to maltose
How is bicarbonate secretion controlled?
Secretin released in response to acid in the duodenum
How is zymogen secretion controlled?
Stimulated by cholecyokinin which is released in response to fat or amino acids in the duodenum
What is the neural control of pancreatic function?
Vagal and ENS reflexes controlled by arrival of organic nutrients in duodenum
