airway epithelium

The airway epithelium is the wallpaper lining the inside of every breathing tube, from the windpipe down to the small bronchioles. But it is wallpaper that works: this single sheet of cells is both a sealed barrier keeping the outside world out and an active surface that traps and sweeps away whatever you inhale.

It is built from several cell types working as a team. Ciliated cells carry the beating cilia that move mucus; goblet cells and submucosal glands make that mucus; and basal cells act as a reserve that can multiply and replace damaged neighbors. The cells are joined by tight junctions that seal the gaps between them, so the lining is a continuous, defended wall rather than a leaky one.

Beyond its physical and mucociliary roles, the epithelium is a frontline sensor and signaler of immune defense, releasing antimicrobial substances and alarm molecules when it detects pathogens. Because it sits at the interface with inhaled air, it takes the brunt of injury from smoke, viruses, and pollutants, and its damage and faulty repair underlie diseases such as COPD, asthma, and airway scarring.