Epidermal development of fetal porcine skin was studied in fetuses from 41 days of gestation until birth with scanning and electron microscopy techniques as well as histochemical methods, including immunohistochemistry. The porcine fetus develops a relatively thick and solid multilayered cover of epidermal cells, which is not lost before birth. It consists of tightly packed cells of the periderm and the stratum intermedium. The periderm cells are totally filled with filamentous proteins; in the intermediate cells, the filamentous proteins are concentrated in the cell periphery, forming a thick marginal zone. Immunohistochemically, the cytofilaments could be identified as cytokeratins of lower and higher molecular weights. The first thin stratum corneum lamellae are formed below the stratum intermedium at about 80-85 days of gestation.

Histochemical methods for nucleic acids and glycogen were used to study epidermis development from fetal porcine skin in fetuses of 41 days of gestation (d GA) until birth. The development of nucleic acid contents as measured densitometrically in the stratum basale reflects structural changes occurring during epidermis differentiation and is also related to epidermal thickness development. Extinction peaks are followed by an increased production of intermediate cells (about 70 d GA), and the first generation of adult-type, keratinizing epidermal cells (about 80-85 d GA), respectively, which form the first thin stratum corneum lamellae below the stratum intermedium.The glycogen content of fetal porcine epidermis likewise develops in close connection with structural maturation, i. e. it is highest in peridermal and intermediate cells just before the onset of an increased deposition of cytokeratins in these cells at about 67d GA, and later diminishes until birth.