2. Histology-Exocrine Pancreas
• 2 major components – acinar cells and
ducts
• Constitute 80% to 90% of the pancreatic
mass
• Acinar cells secrete the digestive
enzymes
• 20 to 40 acinar cells coalesce into a unit
called the acinus
• Centroacinar cell (2nd cell type in the
acinus) is responsible for fluid and
electrolyte secretion by the pancreas
3. Histology-Exocrine Pancreas
• Ductular system - network of conduits
that carry the exocrine secretions into
the duodenum
• Acinus small intercalated ducts
interlobular duct pancreatic duct
• Interlobular ducts contribute to fluid
and electrolyte secretion along with
the centroacinar cells
4. Physiology – Exocrine Pancreas
• Secretion of water and electrolytes
originates in the centroacinar and
intercalated duct cells
• Pancreatic enzymes originate in the
acinar cells
• Final product is a colorless, odorless,
and isosmotic alkaline fluid that
contains digestive enzymes (amylase,
lipase, and trypsinogen)
5. Physiology – Exocrine Pancreas
• 500 to 800 ml pancreatic fluid secreted
per day
• Alkaline pH results from secreted
bicarbonate which serves to neutralize
gastric acid and regulate the pH of
the intestine
• Enzymes digest carbohydrates,
proteins, and fats
6. Enzymes
• Amylase
– hydrolyzes starch and glycogen to glucose,
maltose, maltotriose, and dextrins
• Lipase
– emulsify and hydrolyze fat in the presence of
bile salts
• Proteases
– essential for protein digestion
– secreted as proenzymes and require
activation for proteolytic activity
7. Histology-Endocrine Pancreas
• Accounts for only 2% of the pancreatic
mass
• Nests of cells - islets of Langerhans
• Four major cell types
– Alpha (A) cells secrete glucagon
– Beta (B) cells secrete insulin
– Delta (D) cells secrete somatostatin
– F cells secrete pancreatic polypeptide
8. Histology- Islets of Langerhans
• Contain the
cells that
secrete:
• Glucagon -
alpha cells,
20% of cells
• Insulin - beta
cells, 70% of
cells
• Somatostatin -
delta cells, 5%
of cells
9. Endocrine Pancreas
– Secretion is promoted by increased blood
glucose levels
– Stimulates the transport of glucose from
the blood into muscle, liver and adipose
tissue
– Anabolic hormone
• Synthesis of proteins, lipids, and nucleic acids
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10. Endocrine Pancreas
• Glucagon
– Secretion is promoted by decreased blood
glucose levels
• Stimulates the release of Glucose by the
liver
• Catabolic hormone
– Stimulates glycogenolysis, gluconeogenesis,
and lipolysis
• Somatostatin
– Regulates alpha and beta cell secretions
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