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How does interstitial fluid become lymph?

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Diagram of the human lymphatic system highlighting lymphatic vessels and major lymphoid organs, including lymph nodes, adenoids, tonsils, thymus gland, spleen, appendix, bone marrow, and ducts. — lymphatic system The human lymphatic system, showing the lymphatic vessels and lymphoid organs.

Interstitial fluid becomes lymph when it enters the lymphatic system through tiny, highly permeable lymphatic capillaries located in the interstitial spaces between cells.12

As blood circulates, blood plasma leaks through the thin walls of blood capillaries into the surrounding tissues, providing cells with essential nutrients, oxygen, and glucose. While most of this fluid seeps back into the bloodstream, a portion remains in the tissues along with particulate matter, waste products, and large proteins that are too bulky to reenter the blood capillaries.314

Once this extracellular fluid passes into the lymphatic capillaries, it is officially referred to as lymph. From there, the lymph is transported through a network of lymphatic vessels, where it is filtered by lymph nodes before eventually being returned to the circulatory system.1234