What is the primary component of lymph?

The primary component of lymph is interstitial fluid, which plays a crucial role in the lymphatic system. This fluid is derived from the blood plasma that filters out of capillaries into the spaces between cells, where it bathes and nourishes the surrounding tissues. As this fluid accumulates in the interstitial space, it contains water, proteins, and various immune cells, including lymphocytes, which are integral to the body’s immune response.

The lymphatic system collects this interstitial fluid, now referred to as lymph, and transports it through lymphatic vessels back into the bloodstream, facilitating the removal of waste products and supporting immune functions. This makes option A the most accurate description of what constitutes lymph, highlighting its role in maintaining fluid balance and contributing to immune surveillance. Other potential components mentioned in the incorrect choices, such as red blood cells, oxygen, carbon dioxide, hormones, and neurotransmitters, do not make up lymph itself, which is primarily focused on the elements present in interstitial fluid.