Epithelium of the Respiratory Tract

Abstract

The upper part of the respiratory tract functions as an air-conducting system. Here, warming and moistening of the inhaled air and removal of inhaled particles occurs. It is lined by the pseudostratified respiratory epithelium, which consists of four cell types: (1) columnar ciliated cells, which possess cilia that project from their apical plasma membrane and function in the autonomous, coordinated movement of luminal content; (2) goblet cells (MC in a), unicellular glands synthesizing and secreting mucus, forming part of the mucus blanket, which functions as a lubricant and a protective layer; (3) a small number of neuroendocrine cells (also referred to as Kultschinsky cells), dispersed in the epithelium; and (4) basal cells, which function as stem cells for the regeneration of the respiratory epithelium.