Development of the future respiratory system before birth.

Abstract

Observations such as those reviewed help define the ontogeny of the fetal and neonatal respiratory system. Obviously, the central and motor pathways of the fetal respiratory systems are active 'in utero' and respiration at birth is part of a continuing process. At the time of birth marked changes take place within the respiratory system leading to a stabilization of respiratory activity and alterations in the processes which control the species' response to hypoxia and carbon dioxide. The striking intervention of periods of diaphragmatic silence as term approaches with periods similar to activity state changes within the central nervous system, emphasizes the important role that the higher n..