Which of the following describes the function of lymph

Analyze the question: The question asks about the function of lymph, the fluid that flows through the lymphatic vessels and lymph nodes.

Explain the concept: Lymph is a colourless fluid formed from tissue fluid that drains into lymph capillaries. Its main functions are:

1. Returning excess tissue fluid and proteins to the blood
2. Transporting fats absorbed from the small intestine (via lacteals)
3. Defending the body. Lymph passes through lymph nodes, which contain lymphocytes and phagocytes that filter out and destroy bacteria and other harmful particles.

Evaluate each option:

• A. Temperature regulation: This is mainly the job of the skin, blood vessels and sweat glands, as well as the hypothalamus. It is not a primary function of lymph.
• B. Production of antibodies: Antibodies are made by B-lymphocytes (plasma cells). These cells are found in lymph nodes, but the lymph fluid itself does not produce them. This is a function of the cells, not of the lymph.
• C. Engulfing: Phagocytosis is done by white blood cells such as macrophages and neutrophils. This is a process, not the general function of lymph.
• D. Body defence: Lymph carries lymphocytes and passes through lymph nodes, where germs are filtered and destroyed. This is the broad, general function of the lymphatic system, and it covers both antibody production and engulfing.

Body defence is the umbrella function, while B and C are specific mechanisms that contribute to it.

Exam tip: When a question asks for the "function" of lymph, think of "D-F-F": Defence, Fluid return, Fat transport. If "defence" appears among the options, it is usually the best answer.