1. Plasma of blood is filtered by blood capillaries and passes into interstitial spaces as interstitial fluid
2. Interstitial fluid passes from interstitial spaces into lymphatic capillaries, becoming lymph
3. Lymph is drained by lymphatic capillaries into lymphatic vessels with one-way valves
4. Lymph passes through lymph nodes where antigenic microorganisms, foreign substances, or cancer cells stimulate lymphocytes
5. Macrophages phagocytize the attacked foreign substances
6. Efferent vessels leave nodes and pass on to other lymph nodes or lymphatic trunks
7. Lymph flow is enabled by skeletal muscle contractions, respiratory movements, and smooth muscle contraction in lymphatic vessels