Anatomy

Pancreatic Islets

Anatomy

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Eponym: Islets of Langerhans

Structure:

The pancreatic islets are micro-organs scattered throughout the pancreas and composed of highly vascularised clusters of endocrine cells.[1,2] These cell clusters are embedded within the exocrine pancreatic tissue and are supplied by a dense capillary network that facilitates rapid hormone release into the circulation.[1] The principal cell types within the pancreatic islets include insulin-secreting β-cells, glucagon-secreting α-cells, and somatostatin-secreting δ-cells.[2] A smaller population of pancreatic polypeptide-secreting g-cells and ghrelin-secreting e-cells is also present.[3] Islet distribution varies regionally within the pancreas, with the body andtail containing nearly twice as many islets as the head region.[4]

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Function:

The pancreatic islets serve an essential endocrine function by secreting hormones directly into the bloodstream, primarily insulin, glucagon, and somatostatin.[1,5] Insulin lowers blood glucose levels by promoting cellular glucose uptake and storage, whereas glucagon increases blood glucose levels by stimulating glycogen breakdown and gluconeogenesis.[6] Through the coordinated actions of these hormones, the pancreatic islets play a central role in maintaining glucose homeostasis.[1] Dysfunction or destruction of islet cells is a key feature in the pathophysiology of diabetes mellitus, underscoring the clinical significance of these endocrine structures.[4]

References:

Olaniru OE, Persaud SJ. Identifying novel therapeutic targets for diabetes through improved understanding of islet adhesion receptors. Curr Opin Pharmacol. 2018;43:27-33. doi:10.1016/j.coph.2018.07.009
Kim A, Miller K, Jo J, Kilimnik G, Wojcik P, Hara M. Islet architecture. Islets. 2009;1(2):129-136. doi:10.4161/isl.1.2.9480
Ionescu-Tirgoviste C, Gagniuc PA, Gubceac E, et al. A 3D map of the islet routes throughout the healthy human pancreas. Sci Rep. 2015;5(1):14634. doi:10.1038/srep14634
Wang X, Misawa R, Zielinski MC, et al. Regional Differences in Islet Distribution in the Human Pancreas - Preferential Beta-Cell Loss in the Head Region in Patients with Type 2 Diabetes. PLoS One. 2013;8(6):e67454. doi:10.1371/journal.pone.0067454
Moore KL, Dalley AF, R. AAM. Clinically Oriented Anatomy. Wolters Kluwer; 2018.
Pancreas functions, location & disease. Columbia Surgery. Accessed November 29, 2024. https://columbiasurgery.org/pancreas/pancreas-and-its-functions