Alveolenzellen

Alveolenzellen (Alveolar cells) are the primary cell types that constitute the alveolar walls in the lungs and are essential for the gas exchange function of the respiratory system. They are divided into two major subtypes. Alveolarkernzellen (Type I pneumocytes) are large, flattened cells covering about 95 % of the alveolar surface and provide a thin, continuous barrier that allows rapid diffusion of oxygen and carbon dioxide between the air in the alveoli and the blood in the pulmonary capillaries. Type II pneumocytes constitute approximately 5 % of the alveolar epithelium. They are cuboidal, produce pulmonary surfactant, and serve as progenitor cells that can proliferate and differentiate into Type I cells during alveolar repair and regeneration.

The structural arrangement of alveolocytes is tightly regulated by a complex matrix of extracellular proteins and intercellular junctions, ensuring mechanical stability of the alveolar walls and maintaining the surface tension required for efficient ventilation. The production of surfactant by Type II cells is crucial for lowering surface tension, thereby preventing alveolar collapse at end-expiration and minimizing the work of breathing.

Dysfunction of alveolocytes underlies a variety of respiratory diseases. Injury to Type I cells can lead to impaired gas exchange and chronic interstitial lung disease, whereas dysfunction of Type II cells is implicated in surfactant deficiencies and acute respiratory distress syndrome. Recent research focuses on the regenerative capacity of Type II cells and potential therapeutic strategies to modulate their behavior in lung injury and fibrosis.