Chapter 9 - Physical, Endocrine and Growth Factors in Lung Development

Abstract

This chapter describes the physical, endocrine, and growth factors involved in development of the lung. Fetal lung development is a consequence of a complex interaction between various mechanical and endocrine factors. Fetal lung liquid plays an integral role in the development of the lung before birth by maintaining the lungs in a constantly distended state. By maintaining the fetal lungs in a distended state, fetal lung liquid is thought to be essential for fetal lung growth and maturation by acting as an internal "splint" for lung tissue. The basal degree of lung expansion and fetal breathing movements (FBM) are considered to be important physical factors that influence fetal lung growth and development. The basal degree of fetal lung expansion is determined by the volume of liquid retained within the future airways. Circulating endocrine factors as well as paracrine growth factors mediate, potentiate, integrate, and regulate the lung growth in response to these physical factors. The maturational changes induced by corticosteroids are essential for the independent survival of the newborn, although the precise mechanisms involved remain largely unknown. The reported effects of corticosteroids on lung development include those on growth, tissue remodelling, type-II alveolar epithelial cell (AEC) and the surfactant system, and the reabsorption of lung liquid.