Prenatal development of the adrenal gland in the pig (Sus scrofa domestica). Part I. The differentiation and development of the adrenal cortex primordium in the first half of pregnancy

Abstract

The differentiation and development of the adrenal gland in pig embryos from 18 to 48 days of pregnancy were investigated with histological and histochemical methods and in electron microscope. Primordia of the adrenal cortex appear at 21st day as two symmetrical streaks of the condensed mesenchymal cells between the mesonephros, aorta dorsalis and mesenterium. The capillaries and chromaffinoblasts penetrate the primordium. The mesenchymal cells differentiate into adrenal cortical cells. In the differentiating cells both, rough and smooth endoplasmic reticulum as well as the number of mitochondria increase. The shape of the cells changes and their projections transform into microvilli. The fetal cortical cells have features of the steroidogenic cells with abundant SER in whorls and numerous mitochondria with tubular cristae. The giant mitochondria and dense lamellar bodies were observed in these cells. The microvilli on cell surfaces form a microlabirynth in intercellular and perivascular spaces.