Final answer:
Interstitial fluid (IF) is the solution that surrounds and bathes the cells of multicellular animals. It provides nutrients to cells and helps remove waste. Lymph is considered a part of interstitial fluid, and it helps return protein and excess fluid back to the circulation.
Step-by-step explanation:
Interstitial fluid (IF), also known as tissue fluid or intercellular fluid, is a solution that surrounds and bathes the cells of multicellular animals. It is the main component of the extracellular fluid (ECF), along with blood plasma and transcellular fluid. Interstitial fluid provides the cells with nutrients and helps remove waste.
The composition of interstitial fluid can vary depending on the exchange between the tissue cells and the blood. It contains amino acids, sugars, fatty acids, coenzymes, hormones, neurotransmitters, salts, and waste products from the cells. However, it lacks plasma proteins present in blood.
Lymph is considered a part of interstitial fluid and plays a role in returning protein and excess interstitial fluid back to the circulation through the lymphatic system.