Trachea: anatomy and physiology.

The windpipe (trachea) is a tube of 12 cm length connecting the larynx to the principal bronchi that lead to the lungs. The main functions of the trachea comprise air flow into the lungs, mucociliary clearance, and humidification and warming of air. Mucociliary clearance is achieved by kinocilia and goblet cells in the mucosa, and by tracheal glands. The trachea develops from the endodermal lining of the foregut in interaction with the visceral mesoderm. During adult life, different types of stem cells reside in the mucosal epithelium and glandular ducts. Recently, cholinergic chemosensory cells have been described in the trachea.