Fish Diseases and Management

2.2.18 Pancreas

The pancreas has two separate organs

1) Exocrine pancreas

2) Endocrine pancreas

1) Exocrine pancreas

It is directly associated with digestive system which helps in digestion by producing enzymes like lipase, amylase, typsinogen, chymotrypsinogen which is produced in inactive form and are activated by certain enzymes.

2) Endocrine pancreas

It produces hormone for different functions; the main hormones are glucagon secreted by a cells and insulin secreted by b cells.

Inflammation of pancreas is known as pancreatitis. 

Pathology

1. Exocrine pancreas

a) Acinar necrosis

Focal necrosis  normally occurs in association with a number of conditions but the most significant and the most acute are the viral conditions. It leads to the loss of control on production of enzyme in pancreatic tissue. Uncontrolled production of enzymes cause lysis of organelles and release granules which cause necrosis of pancreas. This may happen due to bacterial infection and viral infection especially IPNV(-Infectious pancreatic necrosis virus) which causes damage to pancreas and lead to fatal problem. This happens mostly in temperate water fishes like salmon and trout.

b) Pancreatic Atrophy

Shrinkage in size of pancreatic cell by loss of cell substance is called pancreatic atrophy. In case of chronic pancreatits such as IPN, individual acinar cells become pyknotic and generally undergo autolysis with little in the way of cellular response, other then fibrosis. In some cases acinar structure is disturbed, and acini may shrink and become very darkly stained. In case of Pancreas disease or polymyopathy syndrome of salmon there is loss of exocrine secretion into the gut, manifested by failure to digest protein and absence of faecal trypsin.

c) Neoplasia

Uncontrolled production of acinar cells. Neoplasia of pancreatic acini is rare.

2) Endocrine pancreas

The hormone production is altered and this may result in hyperglycemia or diabetes (increased blood glucose level).

3) Peripancreatic lipid tissue- Peritionitis can result in infiltration and fibrosis of the pancreatic lipid tissue, a distinctive infiltrative condition is pansteatitis, where there s acute inflammatory infiltration of all lipid tissue, but particularly the peripancreatic fat. Acini and islets are unaffected but the walls of fat cells are thickened and there is an infiltration of lymphocytes and macrophages.