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Pancreas

Last updated: February 8, 2021

Summarytoggle arrow icon

The pancreas is a glandular organ located in the retroperitoneum between the duodenal curvature and the splenic hilum. It has both exocrine and endocrine functions and is anatomically classified into four parts: the head, neck, body, and tail. Because it is embryologically derived from the foregut, the pancreas receives arterial supply from the celiac trunk and its branches. The veins of the pancreas drain into the portal vein and the lymphatics eventually drain into the celiac, superior mesenteric, and splenic lymph nodes. The pancreas receives both sympathetic and parasympathetic innervation via the celiac ganglia. Histologically, the pancreas has two functional structures: the exocrine acinar glands and the endocrine pancreatic islets. The exocrine glands produce digestive enzymes, which are secreted into the duodenum, and the endocrine islets produce blood glucose-regulating hormones such as insulin and glucagon, which are secreted into the blood.

Overview

Anatomical subdivisions of the pancreas [1][2]

The uncinate process is posterior to the superior mesenteric vessels. The head, body, and tail of the pancreas lie anterior to the superior mesenteric vessels.

Pancreatic ducts [1][2]

Tumors in the pancreatic head often cause bile duct obstruction and can manifest with painless jaundice (Courvoisier sign).

Gallstones that block the ampulla of Vater can result in both pancreatitis and cholangitis (double duct sign).

Vasculature, lymphatics, and innervation of the pancreas [1][2]

Exocrine pancreas [1]

Histologically, the exocrine pancreas closely resembles the salivary glands. However, unlike the salivary glands, the pancreatic exocrine glands lack myoepithelial cells in the acini and do not possess striated ducts. Additionally, centroacinar cells are unique to the pancreas.

Endocrine pancreas [1]

Beta cells, which are located on the INSide of islets of Langerhans, produce INSulin.

Pancreatic ducts [1]

Exocrine secretions

The pancreatic fluid is isotonic. It contains the following:

Cystic fibrosis is caused by a defective chloride channel that impairs pancreatic water and electrolyte secretion. This results in obstruction of the pancreatic ducts, with subsequent maldigestion and malabsorption.

Feedback mechanisms

Acute pancreatitis leads to activation of the pancreatic enzymes within the pancreatic ducts, which also leads to subsequent autodigestion of pancreatic tissue.

Elevations in serum lipase and amylase can be seen in acute pancreatitis.

Main endocrine cell types and hormones produced

Overview of islets of Langerhans cell types
Cell types Substance secreted Function Stimulation Inhibition
α-cells
  • Glucagon
  • Hypoglycemia
β-cells
δ-cells
ε-cells
  • Intake of food
PP cells (formerly γ-cells)
  • Pancreatic polypeptide
  • ↑ Gastric secretion of gastric acid
  • ↓ Pancreatic exocrine secretions
  • Promotes satiety
  • Intake of food

Insulin synthesis and regulation

C-peptide is released by the β-cells in an equimolar proportion to insulin but is not present in exogenous insulin. It can, therefore, be used to differentiate between endogenous (e.g., insulinoma, sulfonylurea use) and exogenous hyperinsulinism.

Oral glucose results in a greater increase in insulin levels than IV administration.

Exocrine pancreas

Endocrine pancreas

Embryology of the pancreas

  1. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
  2. Chung KW, Chung HM. Gross Anatomy. Lippincott Williams & Wilkins ; 2012
  3. Thukral C, Freedman SD. Annular Pancreas. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/annular-pancreas.Last updated: March 29, 2017. Accessed: November 24, 2018.
  4. Le T, Bhushan V,‎ Sochat M, Chavda Y, Zureick A. First Aid for the USMLE Step 1 2018. McGraw-Hill Medical ; 2017
  5. Insulin biosynthesis, secretion, structure, and structure-activity relationships.
  6. Rorsman P, Braun M. Regulation of Insulin Secretion in Human Pancreatic Islets. Annu Rev Physiol. 2013; 75 (1): p.155-179. doi: 10.1146/annurev-physiol-030212-183754 . | Open in Read by QxMD
  7. Muscelli E, Mari A, Natali A, et al. Impact of incretin hormones on β-cell function in subjects with normal or impaired glucose tolerance. Am J Physiol Endocrinol Metab. 2006; 291 (6): p.E1144-E1150. doi: 10.1152/ajpendo.00571.2005 . | Open in Read by QxMD
  8. Winzell MS, Ahrén B. G-protein-coupled receptors and islet function—Implications for treatment of type 2 diabetes. Pharmacol Ther. 2007; 116 (3): p.437-448. doi: 10.1016/j.pharmthera.2007.08.002 . | Open in Read by QxMD
  9. Prentki M, Madiraju SRM. Glycerolipid/free fatty acid cycle and islet β-cell function in health, obesity and diabetes. Mol Cell Endocrinol. 2012; 353 (1-2): p.88-100. doi: 10.1016/j.mce.2011.11.004 . | Open in Read by QxMD
  10. Nuttall FQ, Gannon MC, Wald JL, Ahmed M. Plasma glucose and insulin profiles in normal subjects ingesting diets of varying carbohydrate, fat, and protein content.. J Am Coll Nutr. 1985; 4 (4): p.437-450. doi: 10.1080/07315724.1985.10720086 . | Open in Read by QxMD
  11. Holst JJ, Gromada J. Role of incretin hormones in the regulation of insulin secretion in diabetic and nondiabetic humans. Am J Physiol Endocrinol Metab. 2004; 287 (2): p.E199-E206. doi: 10.1152/ajpendo.00545.2003 . | Open in Read by QxMD
  12. Philippe J. Somatostatin Inhibits Insulin-Gene Expression Through a Posttranscriptional Mechanism in a Hamster Islet Cell Line. Diabetes. 1993; 42 (2): p.244-249. doi: 10.2337/diab.42.2.244 . | Open in Read by QxMD
  13. Schilsky ML. Wilson disease: Epidemiology and pathogenesis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/wilson-disease-epidemiology-and-pathogenesis?source=see_link.Last updated: January 13, 2015. Accessed: January 6, 2017.
  14. What is pancreatic cancer?. http://www.cancer.org/cancer/pancreaticcancer/detailedguide/pancreatic-cancer-what-is-pancreatic-cancer. Updated: April 5, 2016. Accessed: January 11, 2017.