pseodostratificerede

Pseudostratified epithelium is a type of epithelial tissue that, despite its name, generally forms a single layer of cells resting on the basement membrane. The cells have nuclei at different heights, which gives the appearance of multiple layers, but every cell typically contacts the basement membrane. The most common form is pseudostratified columnar epithelium, and many of its cells are ciliated with interspersed goblet cells that secrete mucus.

Locations and varieties vary. Pseudostratified ciliated columnar epithelium lines most of the respiratory tract, including the trachea and larger bronchi, where cilia move mucus toward the pharynx. Non-ciliated variants occur in parts of the male reproductive system, such as some ducts, and in certain regions of the nasal cavity. Across tissues, there can be a mix of tall columnar cells, shorter cells, and basal stem cells that replenish the epithelium.

Functions include protection of underlying tissues, lubrication, mucus production, and, in ciliated forms, propulsion of mucus and trapped particles toward the throat. The cilia and goblet cells work together to maintain mucociliary clearance, a key defense mechanism of the airway.

Development and clinical relevance. The tissue arises from a single layer of progenitor cells that differentiate into diverse cell types while maintaining contact with the basement membrane. Metaplastic changes can occur with chronic irritation (for example, smoking), where pseudostratified epithelium may transition to a stratified squamous type, reducing mucociliary function and increasing infection risk.

Terminology. The term pseudostratified refers to appearance rather than true layering. In Danish, the tissue is described as pseudostratificeret; the English equivalent is pseudostratified epithelium.