Gastric motility and pancreatic function Flashcards
What produces peristaltic waves?
- Peristaltic rhythm (~3/min) generated by pacemaker cells (longitudinal muscle layer)
- Slow waves - spontaneous depolarisation/repolarisation
- Slow wave rhythm = basic electrical rhythm (BER)
What neural and hormonal factors control motility?
Gastrin ==> increases contraction
Distension of stomach wall ==> long/short reflexes ==> increased contraction
Fat/acid/amino acid/hypertonicity in duodenum ==> inhibition of motility
What secretes bicarbonate in the duodenum?
Bicarbonate (HCO3) secretion from Brunner’s Gland duct cells (submucosal glands) in the duodenum
What is the endocrine action of the pancreas?
Insulin and glucagon and somatostatin
What is the exocrine action of the pancreas?
Exocrine portion (release substances to exterior of the body, lumen of the duodenum) – triangular acinar cells form lobules. Lobules are connected by intercalated ducts to form intralobular ducts → interlobular ducts → main pancreatic duct. This fuses with the common bile duct to form the hepatopancreatic ampulla (Sphincter of Oddi) which releases both pancreatic substances and bile into the duodenum
What is the function of exocrine pancreas?
o Secretion of bicarbonate by columnar duct cells
o Secretion of digestive enzymes by triangular acinar cells
Where are digestive zymogens stored?
Triangular acinar cells of pancreas
What converts zymogens into their active form?
- Enterokinase (produced by and bound to brush border of duodenal enterocytes) converts trypsinogen from the pancreas to trypsin
- Trypsin converts all other zymogens to active forms
What is enterokinase and where is it produced?
Duodenal enterocyes, converts pancreatic trypsinogen to trypsin
What are the 6 categories of pancreatic enzymes?
- Proteases – cleave peptide bonds via hydrolysis e.g. trypsin
- Nucleases – hydrolyse DNA/RNA
- Elastases – collagen digestion
- Phospholipases – phospholipids to fatty acids
- Lipases - triglycerides to fatty acids and glycerol
- α-Amylase – starch to maltose and glucose
What stimulates bicarbonate secretion from the small intestines?
Secretin
What stimulates secretin secretion for acid neutralisation by bicarbonate?
Presence of acid in the duodenum
What stimulates zymogen secretion by the pancreas?
Cholocystokinin (CKK) from the duodenum
What causes CKK release?
Presence of fatty acids and protein in the duodenum
