VPB 121: Veterinary Physiology - II (2+1)

PANCREAS

• Pancreas  has both endocrine and exocrine portions. The endocrine portion of the pancreas is made up of islets of langerhans, secrets hormones like gulcagon (alpha cells), insulin (beta cells) and somatostatin (delta cells) into the blood. The  major portion of pancreas is exocrine in function.

 

• Secretions
  • The enzymes of the pancreatic juice are synthesized and secreted by the acinar cells.
  • The small duct system contain high level of carbonic anhydrase is responsible for the secretion of water and electrolytes.
  • In most species, the pancreatic duct empties directly into duodenum.
  • Horse, dog and fowl usually have two pancreatic ducts.
  • In sheep, pancreatic duct joins with common bile duct before entering into duodenum.
• Composition of pancreatic juice
  • Pancreatic juice is a clear alkaline fluid made up of the secretions of  two separate phases , aqueous and organic phases
  • The aqueous phase causes a higher concentration of HCO₃ and lesser amounts of Cl. The HCO₃ is important for partial neutralisation of the acid chyme from the stomach and  maintenance of H⁺ ion concentration suitable for digestive activities of pancreatic enzymes.

• The organic phase produces more of pancreatic enzymes.  The amount of juice secreted in Horse – 10 to 12, Cattle – 3 to 5, Sheep – 0.5 to 1 L /100kg body weight/day

Pancreatic enzymes

• There are three major groups of enzymes namely proteases, lipases and amylase capable of digesting proteins, fats and carbohydrates respecively. 
• The following proteolytic enzymes of pancreas are secreted as zymogen granaules or proenzymes.
  • Trypsinogen
  • Chymotrysingon
  • Procarboxy peptidase  A and B
  • Proelastase.
• Trypsingoen is converted to active trypsin either by  the action of an enzyme enterokinase present in duodenal and jejunal juice or by autocatalysis.
• Chymotrysingoen, procarboxy peptidases and proelstases are activated by trypsin.
• Trypisn, elastase and chymotrypsin are endopeptidases; carbodxy pepetidase is a exopeptidase.
• Pancreatic amylase (amylopsin) is secreted as an active state. It acts on starch and produces oligosacharides and maltose. It requires an optimum pH of 6 to 9 and chloride ions for this action.
• Pancreatic lipase (steapsin) is secreted as an active form.It splits fats into free fatty acids and glycerol. Calcium ions, polypeptides, peptidees and bile salts enhance lipase activity.
• Cholesterol esterase and phospholipase act on choleterol esters and phospholipids producing non-esterified fatty acids, cholesterol and lysophospholipid.
• Ribonuclease and deoxy ribonuclease present in pancreatic juice reduce ribose nucleic acid and deoxy ribonucleic acids to mononucleotides.