HISTOLOGICAL AND ULTRASTRUCTURAL FEATURES OF PANCREATIC ISLETS AND THEIR ROLE IN ENDOCRINE REGULATION

The pancreatic islets of Langerhans represent highly specialized endocrine microstructures responsible for maintaining glucose homeostasis and coordinating metabolic regulation. Their histological organization, cellular heterogeneity, vascular architecture, and ultrastructural characteristics are closely associated with the synthesis, storage, and secretion of pancreatic hormones. This article examines the histological and ultrastructural organization of pancreatic islets, emphasizing the morphological and functional characteristics of beta, alpha, delta, pancreatic polypeptide-producing, and epsilon cells. Particular attention is devoted to the relationship between endocrine cell distribution, secretory granules, mitochondrial activity, capillary networks, and intercellular communication. The study is designed as a narrative review using descriptive, comparative, and morphological-functional approaches. The analysis demonstrates that pancreatic endocrine regulation depends on the coordinated activity of structurally specialized cell populations and their interactions with vascular, neural, and extracellular matrix components. Alterations in islet architecture and cellular ultrastructure are also considered in relation to pancreatic endocrine dysfunction, particularly diabetes mellitus. Understanding these histological mechanisms is essential for interpreting normal endocrine physiology and the morphological basis of metabolic disorders.