What does our lymphatics system do? The lymphatic system can be thought of as a drainage system needed because, as blood circulates through the body, blood plasma leaks into tissues through the thin walls of the capillaries. The portion of blood plasma that escapes is called extracellular fluid and it contains oxygen, glucose, amino acids, and other nutrients needed by cells. The lymphatic system removes this fluid and these materials from tissues, returning them via the lymphatic vessels to the bloodstream, and aids in the detoxification process.