paracelulární

Paracelular refers to something that is outside or beside a cell. It is a term used in biology and medicine to describe substances or structures located in the intercellular space, which is the region between cells. This space is not empty but contains various components, including extracellular matrix, interstitial fluid, and cellular debris.

The paracelular pathway is a route for substances to move across an epithelial or endothelial barrier. Instead of passing through the cells themselves (the transcellular pathway), substances can move through the junctions between cells, known as tight junctions and adherens junctions. The permeability of the paracelular pathway is regulated by these junctions, which can open or close to control the passage of molecules. This regulation is crucial for maintaining tissue homeostasis, absorbing nutrients, and preventing the entry of harmful substances.

In pathological conditions, the paracelular pathway can become compromised. For example, in inflammation, the junctions between cells may loosen, leading to increased paracelular permeability. This can result in the leakage of fluids and inflammatory cells into tissues, contributing to swelling and tissue damage. Therapeutic strategies sometimes aim to modulate paracelular permeability to either enhance or restrict the passage of substances across barriers.