Interstitium

[2] The interstitial compartment is composed of connective and supporting tissues within the body – called the extracellular matrix – that are situated outside the blood and lymphatic vessels and the parenchyma of organs.

[2][3] The role of the interstitium in solute concentration, protein transport and hydrostatic pressure impacts human pathology and physiological responses such as edema, inflammation and shock.

[4] The non-fluid parts of the interstitium are predominantly collagen types I, III, and V; elastin; and glycosaminoglycans, such as hyaluronan and proteoglycans, that are cross-linked to form a honeycomb-like reticulum.

The interstitium in the submucosae of visceral organs, the dermis, superficial fascia, and perivascular adventitia are fluid-filled spaces supported by a collagen bundle lattice.

[2] The structure of the gel reticulum plays a role in the distribution of solutes across the interstitium, as the microstructure of the extracellular matrix in some parts excludes larger molecules (exclusion volume).

[2][14] The enhanced permeability and retention effects refers to increased interstitial flow causing a neutral or reversed pressure differential between blood vessels and healthy tissue, limiting the distribution of intravenous drugs to tumors, which under other circumstances display a high-pressure gradient at their periphery.