Lung development

Lung development builds the conducting airways and the thin exchange surface needed for breathing after birth. Growth and branching must be coordinated with cell differentiation, blood vessel development and preparation for air-filled function.

Mechanical conditions are part of the developmental signal. Live imaging and force perturbations linked fetal breathing movements and fluid loading to differentiation of type I alveolar cells, while local growth-factor responses helped other progenitors retain type II alveolar cell identity. This connects cell shape and tissue forces to acquisition of gas-exchange function.^[ref]

Pulmonary hypoplasia is insufficient development of the lungs, leaving too little functional pulmonary tissue for the demands after birth. It describes a developmental outcome rather than one unique cause.

Reduced space for lung growth, altered fluid conditions or impaired developmental signaling can reach that outcome through different routes. The distinction between small immature lungs and inadequate inflation of normally developed tissue follows from separating lung development from the mechanics of later breathing.

Movement before air breathing that contributes to fluid-related mechanical stimulation of the developing lung. Physical loading and mature respiratory function are distinct.

The epithelial lining of pulmonary gas-exchange units, containing differently specialized cell types.

An alveolar epithelial cell with secretory functions including surfactant production and context-dependent progenitor activity.

A thin, extended epithelial cell contributing to the gas-exchange surface. Flattening and molecular differentiation should be measured separately.