Abstract

Pancreases from 123 human embryos and fetuses ranging from 3 weeks to 40 weeks of gestation age were studied. Thirty four cases were examined by immunohistochemical preparations to investigate the temporal development of the pancreatic islet particularly with reference of its origin, time of appearance and interrelation of various types of islet cells. Following results were made. 1) The endocrine cells and the acinar cells both originated from the primitive pancreatic duct cells. 2) Alpha, beta and delta cells began to appear almost simultaneously at 10 weeks og gestation. A, B and D cells, in decreasing order of frequency, were all found in the entire areas of the pancreas. 3) Four types of fetal islets i.e., preimtive, "homologous", bipolar and mantle, could be recognized during development. The latter 3 types first appeared simultaneously at 17 weeks of gestation. They continued to increase in sized and number throughout the fetal life and constituted permanent islets. 4) Two types of islet cells could be distinguished with routine H&E staining after the second trimester. 5) The size of fetal pancreatic islets were rapidly increased between early (64 micrometer) and mid-term (113 micrometer) (p<0.05). 6) The primitive islets were composed of 37.3% of alpha cells, 41.3% of beta cells and 13.4% of delta cells. At mid-term the mantle islets were composed of 36.4% of alpha cell, 42.7% of beta cell and 25.6% of delta cell. At term beta cell was higher value (52.6%) than alpha cell (29.3%) and delta cell (17.6%) (p<0.05).

• Keywords: Pancreatic islet;Development;Pancreas