Final answer:
Interstitial fluid is renamed lymph after entering the lymphatic capillaries. These vessels collect the fluid from tissue spaces and filter it through the lymph nodes, allowing it to re-enter the bloodstream as part of the immune and circulatory processes.
Step-by-step explanation:
Tissue or interstitial fluid is called lymph after it enters lymphatic capillaries. When blood plasma, consisting of water solvent with amino acids, sugars, fatty acids, coenzymes, hormones, neurotransmitters, salts, and waste products, filters through capillaries into the surrounding tissue, the fluid that accumulates is called interstitial fluid.
Lymphatic capillaries, which are spread throughout almost every tissue except the central nervous system, bone marrow, bones, teeth, and cornea, collect the excess interstitial fluid. This fluid, when it enters the lymphatic system, becomes known as lymph. It is similar in composition to the interstitial fluid and contains proteins, waste products, cellular debris, pathogens, and numerous white blood cells, mainly lymphocytes.
The lymphatic system plays a critical role in returning this fluid back to the bloodstream. It helps maintain fluid balance and contributes to the body's immune defense by filtering lymph through lymph nodes, where infectious agents are removed by white blood cells before the clean lymph is returned to the heart via the veins.