This chapter reviews the physiological changes that take place in the lungs at birth and the regulation of these changes. The smooth transition from fetal to extrauterine life is dependent upon the ability of the lung to take over the role of respiratory gas exchange, a function that is performed by the placenta during fetal life. To perform this task the lungs has to grow and mature appropriately during fetal life, they must develop a large internal surface area, which is closely apposed to a large vascular bed to facilitate postnatal gas exchange. For pulmonary gas exchange to commence, a number of important adaptive events must occur at the time of birth. The pulmonary vascular bed, which receives only a small fraction of cardiac output in the fetus, must be able to accept the entire output of the right side of the heart; the ductus arteriosus (DA) that in the fetus shunts blood away from the lungs must close and remain closed. The liquid that occupies the lung lumen is rapidly cleared after birth to allow entry of air into the lungs, although a thin film of liquid must remain to protect the epithelium of the air-filled lung and continuous rhythmic breathing must begin. Many of the changes in lung physiology that occur late in gestation to facilitate the transition to air-breathing are closely linked to the processes that initiate labour. During normal gestation, with labour and delivery occurring at term, the fetal lung is well prepared for its critical role of gas exchange after birth. Both endocrine and physical factors play a major role in preparing the lung for extrauterine function.
|Title of host publication
|Subtitle of host publication
|Development, Aging and The Environment
|Richard Harding, Kent E Pinkerton, Charles G Plopper
|Place of Publication
|Number of pages
|Published - 3 Dec 2003