Gastric Motility and Pancreatic Function Flashcards
What is the direction of peristaltic waves?
Body - antrum
Is there mixing in the body of the stomach?
Thin muscle - weak contraction - no mixing
Where is the powerful contraction in the stomach?
Antrum - thick muscle
What is the result of closure of the pyloric sphincter?
Only a small quantity of gastric content (chyme) enters the duodenum
Antral contents are forced back towards the body which results in further mixing
What generates the peristaltic rhythm?
Around 3 waves per min
•generated by pacemaker cells (in the longitudinal muscle layer)
What causes produces the slow waves?
Spontaneous depolarisation/repolarisation
What is the slow wave rhythm aslo known as?
Basic electrical rhythm
How are slow waves conducted?
Through gap junctions along the longitudinal muscle layer
How does the number of action potentials affect the strength of contraction?
More action potentials meakes a stronger contraction
What is the effect of gastrin on contractility?
Gastrin increases contractility
What is the effect of distension of the stomach on contractility?
Long/short reflexes - increased contractility
What is the effect of Fat/acid/amino acid/hypertonicity in duodenum on motility?
Inhibition of motility
What glands release bicarbonate in the duodenum?
Brunner’s glands (which are submucosal)
How does acid in the duodenum result in HCO3 secretion?
Long (vagal) & short (ENS) reflexes - HCO3 secretion (both act on brunner’s gland)
Release of secretin from S cells, resultant HCO3 secretion
- Secretin - HCO3 secretion from pancreas & liver
- Acid neutralisation - inhibits secretin release (negative feedback control) - When the duodenum receives sufficient bicarbonate, the acidity is reduced, so there is therefore less stimulus for the secretin production (negative feedback)
Where is the head of the pancreas located?
located within curvature of duodenum
What are the three parts of the pancreas?
Head, body and tail
What is the endocrine portion of the pancreas?
Pancreatic islets (islets of langerhans)
Islet cells produce insulin, glucagon and somatostatin (controls secretion of insulin and glucagon)
What is the exocrine portion of the pancreas?
Acinar cells and lobules
What changes occur from the lubules to the duodenum?
Connected by intercalated ducts - intralobular ducts - interlobular ducts - main pancreatic duct - common pancreatic duct - hepatopancreatic ampulla (sphincter of oddi) - duodenum
What is the exocrine portion of the pancreas responsible for?
Digestive function of the pancreas
What are the products of duct cells and acinar cells?
Duct cells - bicarbonate
Acinar cells - digestive enzymes
What is the purpose of the bicarbonate produced by the pancreas?
Bicarbonate keeps the pH high so that the digestive enzymes stay at their optimum pH, they would become denatured in the acidic conditions
What is a zymogen?
An inactive form of an enzyme, they are found in acinar cells and are stored as granules
They prevent autodigestion of the pancreas
How does trypsinogen get converted into trypsin?
•Enterokinase (bound to brush border of duodenal enterocytes) converts trypsinogen to trypsin
What is the effect of trypsin?
Converts all other zymogens to active forms, it is a proteolytic enzyme
What are the categories of pancreatic enzymes?
What stimulates bicarbonate production of the pancreas?
Secretin, which is released in response to acid in the duodenum
What causes the release of zymogens?
Cholecystokinin
When is CCK released?
- In response to fat/amino acids in duodenum
- Also under neural control (vagal/local reflexes) - triggered by arrival of organic nutrients in duodenum
Summary of Secretin and CCK function
