Pseudostratifié

Pseudostratifié is a term used in histology to describe a type of epithelial tissue. It appears stratified, meaning it has multiple layers of cells, because the nuclei of the cells are located at different levels. However, upon closer examination, all of the cells in pseudostratified epithelium actually rest on a common basement membrane, making it a single layer. This creates the illusion of stratification.

This type of epithelium is most commonly found lining the airways of the respiratory system, such as the trachea and bronchi. In these locations, pseudostratified epithelium is often ciliated, meaning it possesses tiny hair-like projections called cilia on its apical surface. These cilia beat in a coordinated manner to move mucus and trapped debris away from the lungs. Goblet cells, which produce mucus, are also frequently interspersed within pseudostratified ciliated epithelium.

The specific appearance of pseudostratified epithelium can vary. The most common type is pseudostratified columnar epithelium, where all cells are columnar or tall and irregular, but their nuclei are at different heights. Variations can include pseudostratified squamous epithelium, although this is less common. The presence of cilia and goblet cells is a key functional characteristic of many pseudostratified epithelial tissues, contributing to their role in protection and clearance.