CorpusHuman Anatomy
RespiratoryTissue

Respiratory epithelium

Also known as: ciliated pseudostratified columnar epithelium, airway epithelium, goblet cells

Ciliated pseudostratified columnar epithelium with goblet cells that lines most of the conducting airways and drives mucociliary clearance.

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Overview

Respiratory epithelium lines the nasal cavity (respiratory region), paranasal sinuses, nasopharynx, most of the larynx, trachea and bronchi. All its cells rest on the basement membrane, but their nuclei lie at different heights, giving a falsely stratified appearance. Cell types: ciliated columnar cells (most numerous; ≈200–300 motile cilia each), goblet cells (mucin secretion), basal cells (stem cells), brush cells (chemosensory) and neuroendocrine (Kulchitsky) cells, which release amines and peptides.

The epithelium becomes progressively shorter distally: simple ciliated columnar, then cuboidal in the bronchioles, where goblet cells are replaced by club cells. Over the vocal folds, the upper epiglottis and the oro- and laryngopharynx it is replaced by non-keratinised stratified squamous epithelium that resists abrasion.

Location

Conducting airways from the nasal cavity to the bronchi (shorter forms in the bronchioles).

Parts & subdivisions

  1. Ciliated cells
    Motile cilia (9+2 axonemes) beat in coordinated waves towards the pharynx.
  2. Goblet cells
    Secrete mucins (MUC5AC, MUC5B) forming the gel layer.
  3. Basal cells
    Progenitor cells for the epithelium.
  4. Neuroendocrine cells
    Origin of carcinoid tumours and small-cell lung carcinoma.

Anatomy

Histology

Ciliated pseudostratified columnar epithelium with goblet cells on a thick basement membrane; underlying lamina propria with seromucous glands (in the trachea and bronchi).

Function

  • Traps particles in mucus and moves them out by ciliary beating.
  • Humidifies the airway and secretes antimicrobial substances (lysozyme, lactoferrin, defensins, secretory IgA).
  • Barrier function via tight junctions.

Clinical significance

Squamous metaplasia

Chronic irritation by tobacco smoke converts ciliated epithelium into stratified squamous epithelium, which cannot clear mucus. Metaplasia is reversible, but it can progress to dysplasia and squamous cell carcinoma.

Primary ciliary dyskinesia

Inherited defects of ciliary dynein arms impair mucociliary clearance: chronic sinusitis, bronchiectasis, otitis and infertility; half of patients have situs inversus (Kartagener syndrome).

Compiled from standard anatomy and physiology references — see the Respiratory System sources. For education only; not medical advice.