The Pancreas

The Pancreas

• A retroperitoneal gland

• About 12–15 cm long and 2.5 cm thick

• Lies posterior to the greater curvature of the stomach

• Consists of a head, a body & a tail

• Usually connected to the duodenum by two ducts

• Head - Expanded portion of the organ near the curve of the duodenum

• Superior to and to the left of the head are the central body and the tapering tail

• Larger ducts

– Pancreatic duct (duct of Wirsung)

– Accessory duct (duct of Santorini)

• Pancreatic juices are secreted by exocrine cells into ducts

• Convey the secretions into the small intestine

• The pancreatic duct joins the common bile duct from the liver and gallbladder

• Enters the duodenum as a dilated common duct called the hepatopancreatic ampulla (ampulla of Vater)

• The ampulla opens on an elevation of the duodenal mucosa known as the major duodenal papilla

• The passage of pancreatic juice and bile - Regulated by a mass               of smooth muscle known as the sphincter of the hepatopancreatic ampulla (sphincter of Oddi)

Histology of Pancreas

• The pancreas is made up of small clusters of glandular epithelial cells

• Acini

– About 99% of the clusters – acini

– Constitute the exocrine portion of the organ

– Secrete a mixture of fluid and digestive enzymes - pancreatic juice

• Pancreatic islets

– The remaining 1% of the clusters, called pancreatic islets (islets of Langerhans)

– Form the endocrine portion of the pancreas

– Secrete the hormones glucagon, insulin, somatostatin & pancreatic polypeptide

• Endocrine pancreatic islets (islets of Langerhans) secrete hormones

• Exocrine acini secrete pancreatic juice

Secretions of Pancreas

Pancreatic juice

• 1200–1500 mL of pancreatic juice

• Clear, colorless liquid

• Consists of water, some salts, sodium bicarbonate, and several enzyme

• Sodium Bicarbonate - Buffers acidic gastric juice in chyme

• Stops the action of pepsin from the stomach

• Creates the proper pH for the action of digestive enzymes in the small intestine

• Pancreatic juice contains enzymes digest:

– Starch - Pancreatic amylase

– Proteins - Trypsin, chymotrypsin, carboxypeptidase, and elastase

– Triglycerides - Pancreatic lipase

– Nucleic acids - Ribonuclease & deoxyribonuclease

• Enterokinase converts trypsinogen to trypsin

• In turn, trypsin acts on the inactive precursors