Lymph is a clear to slightly yellowish fluid that circulates through the lymphatic system, which is part of the body’s immune and circulatory systems.
It originates when blood plasma leaks out of capillaries into the surrounding tissues (this fluid is called interstitial fluid). Most of it is reabsorbed back into the blood, but some enters lymphatic capillaries, becoming lymph.
Water (main component)
Proteins (smaller amount than in plasma)
Lipids (especially after a fatty meal, lymph looks milky and is called chyle)
Lymphocytes (white blood cells crucial for immunity)
Cellular debris, bacteria, and foreign substances picked up from tissues
Fluid Balance – returns excess tissue fluid back to the bloodstream, preventing swelling (edema).
Fat Transport – absorbs fats and fat-soluble vitamins from the intestines and delivers them to the bloodstream.
Immune Defense – carries lymphocytes and antigen-presenting cells to lymph nodes, where pathogens are filtered and immune responses are activated.
Lymph travels in one direction only, from tissues → lymphatic vessels → lymph nodes (for filtering) → larger ducts → finally draining into the venous blood at the subclavian veins.