Where are lymph nodes primarily located and what is their function?

• A. Lymph nodes are located throughout the body, especially in the neck, armpits, and groin; they filter lymph and mount immune responses.
• B. Lymph nodes are located primarily in the heart to regulate blood flow.
• C. Lymph nodes are responsible for oxygen exchange in the lungs.
• D. Lymph nodes produce bile as part of digestion.

Answer: (C)

Lymph nodes are immune system hubs along lymphatic vessels. They are found throughout the body, with noticeable clusters in the neck, armpits, and groin. Their main role is to filter lymph, trapping bacteria, viruses, and other foreign particles, and to activate the immune response by presenting antigens to lymphocytes, helping B cells and T cells mount a defense.

They aren’t located in the heart, they don’t regulate blood flow there, and they aren’t involved in oxygen exchange in the lungs. They don’t produce bile, which is a liver/gallbladder function.