What is the fluid that circulates through the lymphatic system?

The fluid that circulates through the lymphatic system is lymph. Lymph is a clear, yellowish fluid that contains a mixture of interstitial fluid, proteins, and various types of immune cells, such as lymphocytes. It plays a crucial role in the immune system, helping to transport white blood cells to and from lymph nodes, which are critical for the body's immune response.

Lymph originates from the interstitial fluid that bathes the cells of tissues in the body. As this fluid enters the lymphatic vessels, it is transformed into lymph. The lymphatic system is essential not only for maintaining fluid balance within the body but also for absorbing fats and fat-soluble vitamins from the digestive system and contributing to the immune system by filtering lymph through lymph nodes.

Other fluids listed, such as blood plasma, cerebrospinal fluid, and interstitial fluid, have distinct functions and do not circulate specifically through the lymphatic system like lymph does. Blood plasma circulates within the blood vessels, cerebrospinal fluid surrounds the brain and spinal cord providing cushioning, and interstitial fluid is the fluid found in the spaces between cells, which can then become lymph as it enters the lymphatic system.