Interstitielles

Interstitielles is the French term used to describe elements, structures, or processes that relate to the interstitium—the spaces between the components of a tissue, a crystal, or another structural framework. The concept is used across several disciplines to denote what lies in the gaps rather than in the main functional units.

In biology and medicine, the interstitium refers to the connective tissue network and the extracellular fluid that fill the spaces between cells in most tissues. The interstitial compartment contains interstitial fluid, derived from plasma, and components of the extracellular matrix such as collagen and proteoglycans. It supports nutrient and waste exchange, immune surveillance, and tissue architecture. Pathologies involving the interstitium include edema (excess fluid in the interstitial space), interstitial nephritis, interstitial pneumonitis, and fibrosis, in which the interstitium becomes thickened and less compliant. Interstitial cells, such as the interstitial cells of Leydig in the testes, reside in the stroma between functional units and can have hormonal or regulatory roles.

In crystallography and materials science, interstitial describes atoms that occupy the spaces (interstitial sites) in a crystal lattice rather than replacing host atoms (substitutional sites). Small atoms such as carbon in iron or nitrogen in titanium form interstitial solid solutions, altering mechanical properties, diffusion, and strength.

The term also appears in geology and fluid science to denote features within pores or spaces inside solids. Across disciplines, interstitiel concepts emphasize the importance of the spaces between primary components in determining function, behavior, and pathology.