How is tissue fluid different from lymph?

Tissue fluid and lymph are both important components of the body's fluid transport system, yet they have distinct characteristics and differences in their origins and functions.

The correct choice highlights that tissue fluid is derived from blood plasma. It is formed when plasma leaks out of the capillaries into the surrounding tissues, filling the spaces between cells. This process occurs due to hydrostatic pressure and is essential for delivering nutrients and oxygen to cells while removing waste products. On the other hand, lymph is formed when this tissue fluid is collected by lymphatic capillaries. These lymphatic vessels then transport lymph back to the bloodstream, where it eventually re-enters circulation. This choice accurately reflects the process of fluid movement from the blood to the tissues and then into the lymphatic system.

The other options do not accurately capture the distinctions between tissue fluid and lymph. For instance, while proteins are present in tissue fluid, lymph does also contain some proteins, particularly during certain conditions or pathologies. Additionally, tissue fluid does not remain "in the blood"; it exists in the interstitial spaces, while lymph is not merely a filtration outcome but an active collection of interstitial fluid. Finally, tissue fluid is present at all times under normal physiological conditions and is not limited to