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Questions and Answers
What stimulates the release of cholecystokinin (CCK) from the duodenal mucosa?
What stimulates the release of cholecystokinin (CCK) from the duodenal mucosa?
Which of the following physiological abnormalities is NOT associated with pancreatic resection?
Which of the following physiological abnormalities is NOT associated with pancreatic resection?
The primary effect of secretin on pancreatic secretions involves the release of which type of fluid?
The primary effect of secretin on pancreatic secretions involves the release of which type of fluid?
Which nutrient absorption is critically affected by the loss of alkaline pancreatic secretions?
Which nutrient absorption is critically affected by the loss of alkaline pancreatic secretions?
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During which phase is vagal stimulation triggered by the sight and smell of food?
During which phase is vagal stimulation triggered by the sight and smell of food?
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What is the primary role of enterokinase in the activation of pancreatic enzymes?
What is the primary role of enterokinase in the activation of pancreatic enzymes?
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Which ion is exchanged for HCO3− during the secretion of pancreatic fluid?
Which ion is exchanged for HCO3− during the secretion of pancreatic fluid?
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Which enzyme is responsible for cleaving triglycerides into free fatty acids and glycerol?
Which enzyme is responsible for cleaving triglycerides into free fatty acids and glycerol?
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What is the role of co-lipase in pancreatic enzyme function?
What is the role of co-lipase in pancreatic enzyme function?
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During the secretion of pancreatic juice, what contributes to the increase in blood flow via vasodilation?
During the secretion of pancreatic juice, what contributes to the increase in blood flow via vasodilation?
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Study Notes
Exocrine Secretions of the Pancreas
- The pancreas secretes about 1.5 liters of fluid daily, rich in bicarbonate and various enzymes.
- Epithelial cells lining the ducts form the fluid component; bicarbonate (HCO3−) is exchanged for chloride (Cl−).
- Sodium (Na+) and potassium (K+) are exchanged for hydrogen ions (H+) produced by carbonic anhydrase.
- The movement of Na+ and HCO3− creates an osmotic gradient, attracting water.
Enzyme Composition
- Pancreatic enzymes include proteolytic, amylase, and lipolytic, with proteolytic secreted in an inactive form (zymogen granules).
- Key activation step involves converting trypsinogen to trypsin, facilitated by enterokinase from the duodenum in an alkaline environment.
- Activated trypsin subsequently activates other enzymes like chymotrypsinogen, proelastase, trypsinogen, and procarboxypeptidase.
Proteolytic Enzymes
- Chymotrypsin cleaves peptide bonds, elastase cleaves peptide bonds, trypsin cleaves peptide bonds, and carboxypeptidase cleaves at the C-terminus.
Amylase and Lipolytic Enzymes
- Amylase digests starch by cleaving α-1,4-glycosidic bonds; further digestion occurs by small bowel brush-border enzymes.
- Lipolytic enzymes are also secreted in inactive forms and activated by trypsin, including lipase, co-lipase, phospholipase A2, and cholesterol esterase.
Regulation of Exocrine Secretions
- Pancreatic juice secretion is regulated in three phases:
- Cephalic Phase: Vagal stimulation due to sight, smell, and taste of food.
- Gastric Phase: Gastrin and vagal reflex stimulate secretion.
- Intestinal Phase: 60-70% of the stimulus from hormones CCK (increases enzyme-rich fluid) and secretin (increases bicarbonate-rich fluid).
- CCK is stimulated by lipids, while secretin responds to acidity and peptides/amino acids.
Endocrine Secretions
- Detailed examination of endocrine functions, including hormones like insulin, is found in Chapter 12.
Clinical Physiology: Effects of Pancreatic Resection
- Malnutrition: Results from inadequate digestion of proteins and lipids due to loss of enzymes; leads to weight loss and fatty stools.
- Malabsorption: Loss of alkaline secretions fails to neutralize gastric chyme, causing malabsorption of minerals, leading to anemia and osteoporosis.
- Diabetes Mellitus: Complete loss of pancreas results in absolute insulin deficiency.
Liver and Gall Bladder
- Bile Production: Hepatocytes secrete fluid similar to plasma into canaliculi, crucial for digestion.
- Bile production is regulated by cephalic (vagal), gastric (vagal), and intestinal phases (CCK and secretin).
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Description
Test your knowledge on the exocrine functions of the pancreas, focusing on its fluid components and the role of various ions in pancreatic juice. This quiz will cover the mechanisms involved in enzyme secretion and bicarbonate transportation essential for digestion.
