Abstract

The pancreas consists of two types of tissue arising from same primitive cells, but with entirely different functions. Although the adult human pancreas and fetal islet tissue have been the subject of numerous electron microscopic studies, little is known of the ultrastructure of the developing human exocrine pancreas. The purpose of the current study is to investigate development of endo and exocrine of pancreas, especially during the middle trimester of human fetal life, which is the period of acinar cell maturation. Fresh autopsy specimens of pancreas, taken from 15 human fetuses at the 12th (n=2), 13-16th (n=5), 17-20th (n=4), 21-24th (n=2) and 25-28th (n=2) weeks of gestation, were studied electron microscopically, and immunohistochemically. Antisera against insulin, somatostatin, glucagon, pancreatic polypeptide and gastrin, were used for immunohistochemistry. By the 12th week, primitive exocrine acini were identified and these were matured rapidly in the next 6 weeks. At the 17th week stage, ultrastructural examination revealed atypical zymogen granules in the acinar cells. These became progressively less numerous in the 21-28 week period when classical zymogen granules increased upto the level of adult stage. All the endocrine cells were found at the 12th week, forming primitive or mature islets. The relative ratio of endocrine cells at the 12th week was about 35.4%, 24.9%, 39.8%, 0.5% for A, B, D & PP cell, respectively. But at the 25th to 28th week of development, the relative numbers of A and D cells decreased somewhat, whereas those of the B cells increased. The PP cells were constant. The G cells were found at the 12th week of fetal period, which appeared through out the on period.

• Keywords: Development;Pancreas;Ultrastructure;Immunohistochemical;Gastrin;