ependyma

The ependyma is the thin epithelial lining of the brain’s ventricular system and the spinal cord’s central canal. It is formed by ependymal cells that range from simple to pseudostratified cuboidal or columnar in shape, often bearing apical cilia and microvilli. The ependymal layer covers the inner surfaces of the brain ventricles and lines the spinal canal, forming a continuous interface between cerebrospinal fluid and neural tissue.

Histologically, ependymal cells originate from neuroepithelium and are joined by junctions such as gap and, in some regions, tight junctions, which create a selectively permeable barrier. Although not a secretory epithelium like the choroid plexus, the ependyma participates in regulating the composition of cerebrospinal fluid and its movement.

Functions include regulating CSF composition and pressure, and promoting CSF circulation through coordinated ciliary beating. In some mammals, ependymal cells contribute to neural stem cell niches in the subventricular zone, supporting limited neurogenesis during development and in adulthood.

Clinical relevance includes tumors called ependymomas, which arise from ependymal cells and can cause hydrocephalus by obstructing CSF flow. Ependymal damage or inflammation can disrupt CSF dynamics and contribute to hydrocephalus or other CSF-related disorders.