Final answer:
The fluid that enters the lymphatic plexus is known as interstitial fluid, which becomes lymph fluid within the lymphatic system. This system filters the lymph through lymph nodes and eventually returns it to the venous bloodstream.
Step-by-step explanation:
The fluid that enters the lymphatic plexus is referred to as interstitial fluid. Interstitial fluid originates from the 20 liters of plasma that leaks out of the blood capillaries into the spaces between cells daily due to capillary filtration. From this, 17 liters are reabsorbed by the blood vessels, but the remaining three liters enter the lymphatic system, transforming into lymph. This lymph fluid is critical as it transports cells and nutrients while also filtering out foreign substances through lymph nodes before eventually emptying back into the venous bloodstream.
Lymph enters the lymph nodes via afferent lymphatic vessels, passes through germinal centers rich in B cells and other immune cells, collects in the medullary sinuses, and exits the node through efferent lymphatic vessels. The entire lymphatic system, including the spleen and lymph nodes, plays a vital role in maintaining fluid balance, protecting against infection, and absorbing nutrients from the digestive system.