Gastric Motility and Pancreatic Function Flashcards
Where in the stomach is there peristaltic waves?
From body to antrum
Describe gastric motility of the body of the stomach?
Thin muscle so weak contraction so no mixing
Describe the gastric motility of the antrum of the body
Thick muscle so powerful contraction so mixing happens and there is contraction of the pyloric sphincter
What generates peristaltic rhythm?
Pacemaker cells in longitudinal muscle layer
What is the function of contraction of the pyloric sphincter?
Only small quantity of gastric content (chyme) enters the duodenum
Further mixing as products forced back towards body of stomach
Explain slow waves
Spontaneous depolarisation/ repolarisation
Conducted through gap junctions along longitudinal muscle layer
What is the slow wave rhythm?
Basic electrical rhythm (BER) - each part of gut has own
Describe slow waves and strength of contraction
Slow wave depolarisation is sub threshold so need further depolarisation to induce AP
Number of APs determine the strength
Describe neural/ hormonal control on motility
Gastrin
Distention of stomach wall
Fat/acid/amino acid/ hypertonicity in duodenum
How does gastrin effect motility?
Increases contraction
How does distention of stomach wall effect motility?
Triggers long vagus and short enteric reflexes which increases contraction
How does fat/acid/amino acid/ hypertonicity in duodenum effect motility?
Causes inhibition of motility
What neutralises acid in the duodenum?
Bicarbonate secretion from Brunner’s Gland duct cells (submucosal glands)
What is acid in the duodenum broken down into?
Bicarbonate binds with H to create carbonic acid which broken down makes water and CO2
What does acid in the duodenum trigger?
Long vagal and short enteric reflexes innervate Brunner’s gland cells to secrete
Release of secretin from S cells - bicarbonate secretion
Explain the release of secretin
Secretin is released from S cells when acid is in duodenum
Bicarbonate secretion from pancreas and liver
What happens when acid is neutralised?
Inhibits secretin release so negative feedback control
What are the 3 parts of the pancreas?
Head
Body
Tail
Explain the endocrine portion of the pancreas
Has pancreatic islets - islet cells produce insulin and glucagon to control blood glucose conc.
Also produce somatostatin
Explain the exocrine portion of the pancreas
Secrete outside of body
Have acinar cells in lobules
How are lobules connected in the pancreas?
Intercalated ducts - intralobular ducts - interlobular ducts - main pancreatic duct - common bile duct
What control bile secretion from common bile duct into duodenum?
Hepatopancreatic ampulla (sphincter of Oddi)
What happens if main pancreatic duct is blocked?
There is an accessory pancreatic duct
What is the function of the exocrine portion of the pancreas?
Responsible for digestive function of pancreas
Describe the anatomical structure of exocrine pancreas
Acini into ducts into pancreatic duct
What do duct cells in exocrine pancreas secrete?
Bicarbonate
What do acinar cells in endocrine pancreas secrete?
Digestive enzymes
What do acinar cells contain?
Contain digestive enzymes stored as inactive zymogen granules
What is the function of zymogens?
Prevents autodigestion of pancreas
Explain Enterokinase
Bound to brush border of duodenal enterocytes which convert trypsinogen to trypsin
What is the action of trypsin?
Converts all other zymogens to active forms
What are some pancreatic enzyme groups?
Proteases
Nucleases
Elastases
Phospholipids
Lipases
Alpha-amylase
What is the function of proteases?
Cleave peptide bonds
What is the function of nucleases?
Hydrolyse DNA/RNA
What is the function of elastases?
Collagen digestion
What is the function of phospholipidases?
Breaks down phospholipids into fatty acids
What is the function of lipases?
Triglycerides to fatty acids and glycerol
What is the function of alpha-amylase?
Starch to maltose and glucose
What is bicarbonate secretion stimulated by?
Secretin secreted from S cells in response to acid in the duodenum
What is zymogen secretion stimulated by?
Cholecystokinin (CCK) which is released in response to fat/ amino acids in duodenum
Also under neural control by arrival of organic nutrients in duodenum
