Blood, the carrier of nutrients, wastes, and gases, circulates within blood vessels through the body, exchanging materials with the interstitial fluid.
Interstitial fluid, formed by filtration from blood, is the fluid surrounding body cells in the tissue spaces and is essential to proteinless plasma.
Lymph is the protein-containing fluid that enters the lymphatic capillaries (from the tissue spaces); hence, its composition is the same as that of the interstitial fluid.
