Pancreas

The pancreas is a mixed exocrine and endocrine gland situated in the abdominal cavity. It plays vital roles in digestion (exocrine) and hormonal regulation of blood glucose (endocrine).

• Exocrine portion: Produces pancreatic juice rich in digestive enzymes (amylase, lipase, proteases).

• Endocrine portion: Composed of islets of Langerhans that secrete hormones like insulin, glucagon, somatostatin, and pancreatic polypeptide.

Topography and Location

The pancreas is closely associated with the duodenum, lying in the mesoduodenum and between the stomach and small intestine. It varies slightly in position and shape among species.

• Dog and cat: L-shaped, with a right lobe along the descending duodenum and a left lobe near the greater curvature of the stomach.

• Horse: Irregular and triangular, lies between the stomach and the ascending duodenum.

• Ruminants (e.g., cattle, sheep, goats): More compact and lobulated, closely associated with the portal vein and duodenum.

• Pig: Encircles the portal vein and is more ring-shaped.

Gross Anatomy

• Lobes:

  • Right lobe: Lies in the mesoduodenum, equivalent to the head of pancreas in human

  • Left lobe: Embedded in the deep leaf of the greater omentum near the stomach, equivalent to the tail of pancreas in human

  • Body: Connects the two lobes near the pylorus or first part of the duodenum.

• Color: Pinkish to pale tan in live animals.

• Consistency: Firm and lobulated on palpation.

Duct System

Species differences exist in the ductal drainage system:

• Dog: Has both a pancreatic duct (major) and an accessory duct (minor).

• Horse: Typically only one duct, which opens with the bile duct.

• Cattle and pig: Usually only the accessory duct persists.

• Cat: Usually has only the pancreatic duct, entering at the major duodenal papilla.

Microscopic Structure

• Exocrine pancreas:

  • Composed of serous acini with pyramidal cells.

  • Acinar cells produce digestive enzymes stored in zymogen granules.

  • Duct system includes intercalated, intralobular, and interlobular ducts.

• Endocrine pancreas:

  • Contains islets of Langerhans.

  • Islets have several cell types:

    • α-cells: Secrete glucagon.

    • β-cells: Secrete insulin.

    • δ-cells: Secrete somatostatin.

    • PP-cells: Secrete pancreatic polypeptide.

Vascular Supply

• Arterial supply: Derived from branches of the celiac artery and cranial mesenteric artery. Pancreatic branches often accompany the bile duct and portal vein.

• Venous drainage: Primarily to the portal vein, draining into the liver.

• Lymphatic drainage: To hepatic and pancreaticoduodenal lymph nodes.

Innervation

• Sympathetic fibers: From the celiac plexus, modulate blood flow and secretory activity.

• Parasympathetic fibers: From the vagus nerve, stimulate secretion.

• Intrinsic enteric neurons also influence endocrine secretion.