Pancreatic Exocrine Secretions And Control Flashcards
What are the types of cells in the pancreas?
Acinar cells
Pancreatic acini
Duct cells
Pancreatic islet cells
What do pancreatic islet cells secrete?
Hormones
What do duct cells secrete?
NaHCO3
What do pancreatic acini cells form?
The exocrine portion of the pancreas
What do acinar cells secrete?
Digestive enzymes
What effect does CCK have on acinar cells?
Stimulatory- causes them to secrete pancreatic enzymes
What are the levels (smallest -> biggest) of acini -> pancreatic duct?
Acini Sacs Microvilli Intercalated ducts Intralobular ducts Interlobular ducts Pancreatic duct
Where does the pancreatic duct enter the duodenum?
Common bile duct
What are the intercalated ducts in the pancreas made up of?
Squamous epithelium
What are the intralobular ducts in the pancreas made up of?
Cuboidal or low columnar epithelium
What are the interlobular ducts in the pancreas made up of?
Columnar epithelium/ goblet cells
How much fluid does the pancreas secrete per day?
1.5 litres
What is in pancreatic secretions?
Sodium and HCO3- rich, albumin, globulin and digestive enzymes
Why are some enzymes secreted in an inactive form?
To prevent autodigestion
What are inactive enzymes called?
Zygmogens
Where does enzyme activation happen?
Duodenum
What are the anions in pancreatic juice?
HCO3-, Cl-, SO4 2- and HPO4 2-
What are the cations in pancreatic juice?
Na+, K+, Ca 2+, Mg 2+
How is the composition of pancreatic juice modified as it travels through the duct?
Epithelial cells actively exchange Cl- for HCO3 -
H+ actively eliminated by Na +/K+ exchanger, exchanged for K+ by Na+/K+ ATPase and neutralises HCO3 -
What is [HCO3 -] in pancreatic juice and its rate of production inversely proportional to?
[HCO3 -] blood
What decreases in pancreatic juice when secretin increases?
Amylase and chloride ions
What does a secretin stimulated pancreas cause?
[HCO3 -] rich secretions
What are the 5 types of enzyme secretion in the pancreas?
- proteolytic enzymes
- amylase
- lipase
- ribonuclease
- deoxyribonuclease
What does colipase do?
Works with lipase to break down fat droplets
When are enterokinases secreted?
In response to CCK
Where are enterokinases found?
Brush border of epithelial cells
What do enterokinases do?
Trypsinogen -> trypsin
What does trypsin do?
Causes an autocatalytic chain reaction ( autoactivation and activation of other proenzymes)
What are the inhibitors of enterokinases?
KaZal inhibitor, enzyme Y
Intracellular pH of zymogen granule- acidic
What happens in acute pancreatitis?
Trypsin activates phospholipase A2 in the pancreatic duct
What does isolethicin do?
Disruption of pancreatic tissue, membrane damage and necrosis
What does acute pancreatitis lead to?
Increased [pancreatic alpha amylase] in blood
What happens if there is a pancreatic insufficiency of lipase?
Poor digestion and malabsorption of lipids
What are the percentages of pancreas secreted enzymes that reach the small intestine?
Amylase- 75%
Trypsin- 20%
Lipase- 1%
What 4 things control pancreatic secretions?
Neuroendocrine signals, vagal (parasympathetic) stimulation, sympathetic stimulation, secretin and CCK
What happens in the pancreas when the parasympathetic systems stimulated?
Enhances rate of secretion of enzymes and various components of pancreatic juice
What control of pancreatic secretions happen in the cephalic phase?
Vagal stimulation of gastrin release from the antrum -> protein rich pancreatic juice
What control of pancreatic secretions happen in the gastric phase?
Distension, amino acid and peptide stimulated gastrin secretion -> enzyme rich pancreatic juice
What does CCK do to the gall bladder?
Contracts it and relaxes the sphincter of oddi-> release of bile into the duodenum
What happens in the pancreas in cystic fibrosis?
The pancreas has blocked pancreatic ducts and intestines cannot absorb nutrients properly
