Pancreatic Secretion

Overview

• Pancreatic secretions
  • overview
    • exocrine pancreas releases secretions into duodenum of small intestine
      • secretions contain aqueous and enzymatic components
        • aqueous component
          • contains HCO₃^–
            • neutralizes H⁺ delivered to duodenum from stomach
        • enzymatic component
          • contains pancreatic enzymes
            • digest carbohydrates, proteins, and lipids into absorbable molecules
            • lipid digestion begins in the duodenum; however, lipid absoprtion occurs primarily in the jejunum 
  • formation of pancreatic secretions
    • exocrine pancreas organization resembles that of salivary glands
    • acinar cells secrete enzymatic components of pancreatic secretions
      • see Pancreatic Enzymes 
    • centroacinar cells and ductal cells secrete initial isotonic aqueous components of pancreatic secretions
    • ductal cells modify initial isotonic aqueous components by transport processes in ductal epithelial cells
      • modification results in HCO₃^– release into pancreatic secretions and net absorption of H⁺
        • causes acidification of pancreatic blood
      • pancreatic secretions remain isotonic
  • flow rate and composition of pancreatic secretions
    • flow rate changes HCO₃^– and Cl^– concentrations in pancreatic secretions
      • reciprocal relationship
      • at highest flow rates
        • high HCO₃^– and low Cl^–
      • at lowest flow rates
        • low HCO₃^– and high Cl^–