Bodies have continuous reticular networks, comprising collagens, elastin, glycosaminoglycans, and other extracellular matrix components, within and around all organs. Fibrous tissue coverings of nerves and blood vessels create structural continuity beyond organ boundaries. We recently validated fluid flow through human fibrous tissues, though whether these interstitial spaces are continuous through the body or discontinuous, confined within individual organs, remains unlcear. We investigated continuity of interstitial spaces using two approaches. Non-biological particles (tattoo pigment, colloidal silver, anthracotic pigment) were tracked within colon, skin, and lung interstitial spaces and into adjacent fascia. Hyaluronic acid, a macromolecular component of interstitial spaces, was also visualized, analyzing skin and subcutaneous fascia, colon and mesenteric fascia, lung and pleura, gynecologic organs and their fascial sheathes, breast, and heart and great vessels. Both techniques demonstrate interstitial space continuity within and between organs including within perineurium and vascular adventitia traversing organs and the spaces between them. We suggest that there is a body-wide network of fluid-filled interstitial spaces that has significant implications for molecular signaling, cell trafficking, and the spread of malignant and infectious disease.
