The Islets of Langerhans
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Islets of Langerhans, also called islands of Langerhans, irregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates. The islets consist of four distinct cell types, of which three (alpha, beta, and delta cells) produce important hormones; the. The pancreatic islets or islets of Langerhans are the regions of the pancreas that contain its endocrine (hormone-producing) cells, discovered in by.
This brief article will present arguments supporting the view of diabetes as a paracrinopathy of the islets of Langerhans. That of the student, Paul Langerhans, has become famous. Langerhans mostly examined pancreatic glands from rabbits and attempted to describe the different cell types and structures. He produced preparations by injecting dyes into the pancreatic duct and found that some cell groups were not in connection with the ducts.
Sadly, the life of Paul Langerhans was short. He became prosector at the University of Freiburg im Breisgau, contracted tuberculosis, migrated to Madeira for its climate and continued studies on the local natural fauna, but ultimately died in at the age of The islets are innervated and vascularised. For obvious reasons, most studies on the islet as a micro-organ have been performed in rodents. In these species, the microcirculation appears remarkable in its microanatomy and microphysiology.
Furthermore, the blood flow dynamics in the islet are affected by the level of glucose in the blood, with hyperglycaemia increasing and hypoglycaemia decreasing the flow respectively. As analysed in detail by Bosco et al. As discussed by Unger and Orci, 6 if anything, the morphological difference in human islets compared with rodents would tend to increase the possibility of paracrine interactions. The development of sensitive and specific assays for polypeptide hormones has permitted investigation in depth of the mechanisms controlling the release of the products of the various endocrine cells of the islets of Langerhans.
Studies were performed in vivo in numerous species, including man.
In vitro studies were conducted mainly in isolated perfused pancreases and on isolated perifused islets of Langerhans. These studies have provided insight on the many factors — metabolites, hormones, neuronal signals — that control the release of the products of the islet endocrine cells.
For more than three decades, there have been indications that there is co ordination in the releasing mechanisms and that this co-ordination exists within the islets themselves. The periodicity of these pulses is seven to eight minutes. The fact that these pulses occur in isolated islets demonstrates that their origin is in the islets themselves and is independent of external metabolic, hormonal or neuronal signals.
The Cells of the Islets of Langerhans
The nature of the intra-islet signal s co-ordinating the secretion of the various endocrine cells of the islets of Langerhans is still the subject of intense investigation. It is now largely recognised that insulin and glucagon are the key hormonal factors regulating energy metabolism. Insulin, the anabolic hormone, promotes storage of glucose in the form of glycogen in liver and muscle and favours the synthesis of triglycerides in adipose tissue.
Aside from the insulin, glucagon and somatostatin, a number of other "minor" hormones have been identified as products of pancreatic islets cells.
Functional Anatomy of the Endocrine Pancreas
Islets are richly vascularized, allowing their secreted hormones ready access to the circulation. Additionally, they are innervated by parasympathetic and sympathetic neurons, and nervous signals clearly modulate secretion of insulin and glucagon.
Endocrine Pancreas: Introduction and Index. Citations Publications citing this paper.
The Function of the Islets of Langerhans
Developing peptide-based inhibitors of amylin aggregation as a novel treatment for type 2 diabetes Idira Christopher Obasse. Development of proteolytically stable N-methylated peptide inhibitors of aggregation of the amylin peptide implicated in type 2 diabetes.
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References Publications referenced by this paper. A novel peptide in the calcitonin gene related peptide family as an amyloid fibril protein in the endocrine pancreas. Fine structure of islets of Langerhans in insular amyloidosis Per Westermark. Islet amyloid polypeptide, islet amyloid, and diabetes mellitus.