Esame Morfologico Ed Istochimico Della Cute Di Ratto Dagli Ultimi Stadi Dello Sviluppo Embrionale Alla Vecchiaia, Con Speciale Riferimento Alle Relazioni Tra Epidermide E Derma. Analogie Tra La Cute Del Neonato E La Cute Durante Le Prime Fasi Dell'Oncogenesi

Abstract

Dermal changes of rat skin have been studied from the last stages of the fetal development up to old age. They have been related to the development of skin epithelial adnexa. The dermis evolves with the age from an immature, loose and highly cellular connective tissue to a fibrous tissue, through a series of changes affecting the cells and the structurally organized and structureless extracellular component. The histochemical changes of the extracellular structures have been described in relation to the morphological changes. The mucopolysaccharides behaviour has been also described. The evolution of the dermis proceeds from the innermost layers to the superficial ones. At the stage of formation of the epithelial buds which penetrate the underlying dermis to constitute the future skin adnexa, the dermis is loose and, at the level of the proliferating pole of the epithelial buds, the basal membrane and the cellular barrier formed by fibroblasts and fibrocites are lacking. The epithelial proliferation appears to be stopped in the depth by the dermis which becomes gradually fibrous. Around the established cutaneous adnexa, the basal membrane and the cellular barrier become continuous. The above data have been related to the dermal changes occurring during epithelial proliferation due to local treatment with irritating and with carcinogenic substances. They are interpreted in the light of the hypothesis concerned with the importance of the connective changes in the various types of cell growth.