Ciliary

Ciliary refers to cilium or cilia, hair-like projections on many cells that can either move or sense the environment. Cilia arise from basal bodies derived from centrioles and extend as membrane-bound organelles. The core of motile cilia is the axoneme, typically arranged in a 9+2 pattern of microtubule doublets with dynein motors that drive bending, while primary (non-motile) cilia usually have a 9+0 pattern and serve sensory and signaling roles.

Functionally, motile cilia generate directional movement of fluid over tissues, such as clearing mucus from the respiratory tract and propelling ova through the fallopian tubes. In many cells, primary cilia act as cellular antennas for chemical and mechanical signals, participating in pathways such as Hedgehog and Wnt that influence development and tissue homeostasis.

In the eye, the term ciliary is used in reference to the ciliary body, which includes the ciliary muscle and ciliary processes. The ciliary muscle alters lens shape to enable accommodation, while ciliary processes produce aqueous humor and contribute to intraocular pressure regulation. The ciliary epithelium is part of the blood-aqueous barrier.

Clinical relevance centers on ciliopathies, disorders caused by ciliary dysfunction. Examples include primary ciliary dyskinesia (impaired motile cilia leading to chronic respiratory infections and sometimes situs inversus and infertility), polycystic kidney disease, Bardet-Biedl syndrome, Joubert syndrome, and Meckel-Gruber syndrome. Diagnosis can involve electron or light microscopy of ciliary structure, nasal nitric oxide testing, and genetic analysis.