Interstitiums

Interstitium (plural interstitiums) is a term used in anatomy to describe the network of loose connective tissue spaces that surround cells in most tissues and organs. These interstitial spaces are filled with interstitial fluid, a component of the extracellular fluid, and are lined by a mesh of collagen and elastin fibers, proteoglycans, and other components of the extracellular matrix. They lie between cells and the vascular and lymphatic systems and participate in the diffusion of nutrients, waste removal, and mechanical support.

In general anatomy, interstitium refers to these spaces that connect with blood and lymphatic vessels. In 2018, researchers popularized the claim that a body-wide, fluid-filled network in the submucosa of several organs could constitute a previously unrecognized organ, sometimes referred to as the interstitium. The finding sparked interest but also debate. Critics argued that the observed spaces might be artifacts of tissue processing, particularly fixation, and that more evidence is needed to determine whether they represent a distinct organ or a conventional feature of connective tissue.

Functionally, interstitial spaces facilitate exchange of nutrients and waste between cells and the circulatory system, serve as a conduit for cell signaling and immune surveillance, and contribute to tissue mechanics. Interstitial fluid dynamics are influenced by capillary filtration, the extracellular matrix, and lymphatic drainage; disturbances can underlie edema, fibrosis, and altered drug distribution.

See also: Interstitial fluid, extracellular matrix, connective tissue, lymphatic system.