gastric motility and pancreatic function Flashcards
gastric motility at stomach body
thin muscle –> weak contraction –> no mixing
gastric motility at stomach antrum
thick muscle so powerful contraction
mixing
contraction of pyloric sphincter –> small quantity of chyme enters duodenum, further mixing as antral contents forced back towards body
what produces peristaltic waves
peristaltic rhythm (~3/min) generated by pacemaker cells in longitudinal muscle layer
slow waves - spont depol/repol
slow waves
basic electrical rhythm (BER)
slow waves conducted through gap junctions along longitudinal muscle layer
what factors increase gastric motility
gastrin
distension stomach wall –> long/short relfexes
what factors inhibit gastric motility
fat, acid, amino acids and hypertonicity in duodenum
how is acid in duodenum neutralised
bicarbonate secreted from Brunner’s gland duct cells
acid in duodenum triggers
long (vagal) and short (ENS) reflexes –> bicarb secretion
release of secretin from S cells –> bicarb secretion from pancreas and liver
three main parts of pancreas
head
body
tail
endocrine portion of pancreas
iselts of langerhans –> insulin, glucagon, somatostatin
exocrine portion of pancreas
acinar cells –> lobules
lobules connected by intercalated ducts –> intralobular duct –> interlobular duct –> main pancreatic duct –> common bile duct –> sphincter of oddi –> duodenum
function of exocrine pancreas
secretion of bicarbonate by duct cells
secretoin of digestive enzymes by acinar cells
zymogens
inactive pre-cursor of digestive enzymes, stored in acinar cells
prevent autodigestion of pancrease
what converts trypsinogen to trypsin
enterokinase - bound to brush border of duodenal enterocytes
what converts all other zymogens to acive forms
trypsin
proteases
cleave peptide bonds
nucleases
hydrolyse DNA/RNA
elasases
collagen digestion
phospholipases
phospholipids to fatty acids
lipases
triglycerides to fatty acids + glycerol
alpha-amylase
startch to maltose an glucose
what stimulates pancreatic bicarbonate secretion
secretin
what is secretin released in response to
acid in duodenum
what is pancreatic zymogen secretion stimulated by
cholecystokinin (CCK)
what is CCK released in response to
fat/amino acids in duodenum
what happens when secretin is released
inc pancreatic bicarb secretion –> bicarb into small intestine –> neutralisation of intestinal acid
what happens when CCK is released
inc pancreatic enzyme secretion –> flow of enzymes into small intestine –> inc digestion of fats and protien
