[Physiology] Gastric motility and pancreatic function Flashcards
what are the different parts of the stomach
body and antrum
role of the body of the stomach
Thin muscle ⇒ weak contraction
⇒ No mixing
role of the antrum of the stomach
Thick muscle ⇒ powerful contraction
Mixing
Contraction of pyloric sphincter ⇒
what happens on contraction of pyloric sphincter
just prior to closing a small quantity of gastric content (chyme) entering duodenum
Further mixing as antral contents forced back towards body
Peristaltic rhythm
(~3/min) generated by pacemaker cells (longitudinal muscle layer)
Slow waves
spontaneous depolarisation/repolarisation
slow wave rhythm
basic electrical rhythm (BER)
where are slow waves conducted
through gap junctions along longitudinal muscle layer
Slow wave depolarisation sub-threshold
require further depolarisation to induce action potentials ⇒ contraction
what does the number of APs/wave determine
strength of contraction
what effect does gastrin have on contraction
increases contraction
Distension of stomach wall
long/short reflexes ⇒ increased contraction
Fat/acid/amino acid/hypertonicity in duodenum
inhibition of motility
how is acid neutralised in duodenum
Bicarbonate (HCO3) secretion from Brunner’s Gland duct cells (submucosal glands)
what does acid in duodenum trigger
Long (vagal) & short (ENS) reflexes HCO3 secretion
Release of secretin from S cells HCO3 secretion
Secretin also HCO3 secretion from pancreas & liver and therefore into dudeonum from pancreatic duct and bile duct
Acid neutralisation
what does neutralisation of acid do to secretin release
inhibits secretin release from s cells(negative feedback control)
what are the three parts of the pancreas
Head (located within curvature of duodenum), body, tail (extends to spleen)
Endocrine portion
Exocrine portion
Head
(located within curvature of duodenum), body, tail (extends to spleen)
Endocrine portion
pancreatic islets (islets of Langerhans): islet cells produce insulin, glucagon (control [glucose]blood ) and somatostatin (controls secretion of insulin and glucagon)
Exocrine portion
acinar cells lobules
lobule transportation
Lobules connected by intercalated ducts intralobular ducts interlobular ducts main pancreatic duct common bile duct hepatopancreatic ampulla (Sphincter of Oddi) duodenum
exocrine pancreas role
digestive function of pancreas
Anatomical Structure of exocrine pancreas
Acini Ducts Pancreatic Duct
Function duct cells
Secretion of bicarbonate by duct cells
Secretion of digestive enzymes by acinar cells
what do Acinar cells contain
digestive enzymes stored as inactive zymogen granules
what do zymogens prevent
autodigestion of pancreas
Enterokinase
(bound to brush border of duodenal enterocytes) converts trypsinogen to active trypsin
Trypsin
converts all other zymogens to active forms
Proteases
Cleave peptide bonds (stomach acid hydrolyss=is) everywhere else hydrolysis
Nucleases
Hydrolyse DNA/RNA
Elastases
Collagen digestion
Lipases
Triglycerides to fatty acids+ glycerol
α-Amylase
Starch to maltose + glucose
Phospholipases
Phospholipids to fatty acids
Bicarbonate secretion
stimulated by secretin
Secretin
released in response to acid in duodenum
Zymogen
secretion stimulated by cholecystokinin (CCK)
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
