Which organ functions to filter blood and is involved in immune function and storage?

• A. Tonsils
• B. Lymphatic system
• C. Epididymis
• D. Spleen

Answer: (D)

This question centers on an organ that handles blood filtration, supports immune responses, and also stores blood components. The spleen fits all three roles: its red pulp actively filters blood by removing old or damaged red blood cells, recycling iron as needed; its white pulp contains lymphocytes that participate in immune responses against blood-borne pathogens; and it serves as a reservoir, storing platelets and a supply of blood that can be released during demand. The other options don’t combine these functions: tonsils contribute to immune defense in the throat but don’t filter blood or store blood; the epididymis is part of the reproductive system and stores sperm; the lymphatic system is a network that supports immunity and fluid transport but isn’t a single organ that filters blood and stores blood components.