Exocrine Pancreas Flashcards
What is the main function of the exocrine pancreas?
Digestion
Exocrine pancreas is similar to salivary glands. What is the functional anatomy of the exocrine pancreas made up from?
Acini - cavity in gland surrounded by secretory cells
Simple cuboidal epithelium
Several excretory ducts (with cuboidal epithelium lining) combine to make what?
Accessory pancreas ducts
What are the 2 main components of pancreatic juice?
HCO3-
Enzymes
What is the function of HCO3- in pancreatic juice?
Neutralise stomach acid to protect small intestine mucosa
Create correct pH for digestive enzymes
What are the functions of the enzymes in pancreatic juice?
Digest carbohydrates, proteins and fats for absorption in the small intestine
Pancreatic juice has a similar ionic composition to what?
Blood
Describe the ionic composition of pancreatic juice
HCO3- actively transported into duct lumen in exchange for Cl-
Water follows by osmosis
H+ transported into blood (negates alkaline tide)
HCO3- is reabsorbed into acinar cells (when normal flow rate). When high flow rate, not enough time to reabsorbed HCO3- so juice is highly alkaline
Constant Na+/K+
Why are proteases secreted into the stomach in an inactive form?
To prevent auto digestion of the stomach
What does amylase break down?
Starch to maltose
What do lipases/phospholipases break down?
Fats to glycerol and fatty acids
Pancreas juice contains what precursor for the enzyme trypsin?
Trypsinogen
How is trypsinogen converted to trypsin?
By enteropeptidases on the duodenum epithelial surface
What is the function of trypsin? Why do pancreatic cells produce a trypsin inhibitor?
Auto catalysis and activation of other proteases
To prevent auto digestion
What are the three phases of digestion?
Cephalic phase
Gastric phase
Intestinal phase
What is increased throughout all 3 phases of digestion?
Pancreatic juice secretion
What is the cephalic phase mediated by?
Vagus
What is the gastric phase mediated by?
Gastrin
In carnivores, which phases of digestion are enzymatic?
Cephalic
Gastric
In pigs/horses, which phases of digestion are enzymatic and ionic?
Cephalic
Gastric
What is the intestinal phase mediated by?
Secretin / CCK
What inhibits secretin?
Vasoactive inhibitory peptide (VIP)
What is secretin? When is it released?
A hormone released from the duodenum
In response to H+
What does secretin do?
Increase HCO3- secretion
Secretin works by what feedback mechanism?
Negative
As acid chyme is neutralised, stimulus for secretin release decreases
What is cholecystokinin? (CKK) When is it released?
A hormone release from the duodenum
Released in response to fat/protein metabolites
What are fat/protein metabolites?
Components that make up fats/proteins e.g. fatty acids, glycerol, peptides
What does cholecystokinin do?
Increase enzyme secretion
Cause the gall bladder to contract
Cholecystokinin works by what feedback mechanism?
Positive feedback mechanism
Increased enzyme secretion. More fat/protein metabolites which stimulates more CCK release
Physiological features of the exocrine pancreas change between species due to what?
Different eating patterns
Describe the exocrine pancreas and juice secretion in ruminants
Constant secretion
due to constant flow of rumen contents into SI
Describe the exocrine pancreas and juice secretion in carnivores?
Intermittent secretion
Due to intermittent flow of stomach contents to SI
Describe the exocrine pancreas and juice secretion in horses
Continuous secretion as stomach contents flows continuously to SI
However increases more after feeding to allow fermentation
Pancreatic juice in horses is low in HCO3-. How are horses still able to neutralise stomach acid?
Copious secretion of HCO3-
HCO3- secretion by ileum
