Multiciliated

Multiciliated describes cells with numerous cilia on their apical surface. Each cilium is a motile projection that beats in a coordinated fashion to move fluids or particles across the cell surface. In multiciliated epithelia, the cilia are arranged in dense, rhythmically beating fields that drive mucociliary clearance or fluid movement. The term distinguishes these cells from monociliated cells, which bear a single cilium.

Multiciliated cells arise in a process called multiciliogenesis. They amplify centrioles to produce many basal bodies that anchor the cilia at the apical membrane. Transcription factors, notably FOXJ1, orchestrate ciliogenesis, while intraflagellar transport delivers components to the growing cilia. In vertebrates, specialized mechanisms, such as deuterosome-mediated centriole amplification, enable rapid production of dozens of cilia per cell.

In the respiratory tract, multiciliated cells cover the airway epithelium and beat to propel mucus loaded with dust and pathogens toward the pharynx. In the female reproductive system, ciliated cells of the oviduct (fallopian tube) help move the oocyte toward the uterus. In the central nervous system, ciliated cells line the ventricles and contribute to CSF circulation.

Impaired multiciliated cell function underlies primary ciliary dyskinesia (PCD), a genetic disorder characterized by chronic respiratory infections, sinusitis, reduced fertility, and, in about half of cases, situs inversus due to disrupted left–right organizer function. The condition reflects defects in ciliary motility, assembly, or coordination.

Not all cilia are part of multiciliated epithelia; some cells possess a single primary cilium with a sensory role, and some tissues have sparse cilia. Multiciliation is a specialized feature of certain epithelia and is essential for maintaining organ function.