Which of the following are organs in the lymphatic/immune system?

The spleen and thymus are both integral components of the lymphatic and immune systems. The spleen plays a vital role in filtering blood, removing old or damaged red blood cells, and serving as a reservoir for white blood cells, which are crucial for immune responses. It also helps in the production of antibodies and is involved in the body's response to infections.

The thymus, on the other hand, is essential for the development of T-cells, a type of white blood cell that is key to adaptive immunity. During childhood, the thymus is particularly active, providing the environment necessary for T-cells to mature before they are released into the bloodstream to fight off pathogens.

In contrast, the liver and stomach do not belong to the lymphatic and immune systems, as they primarily function in digestion and metabolism. The lungs, while critical for respiration and gas exchange, are not considered part of the immune system despite having immune functions. Lastly, although lymph nodes are pertinent to the lymphatic system by housing lymphocytes and filtering lymph, the liver's primary role does not include a direct function in the lymphatic/immune system. Thus, the spleen and thymus are correctly identified as organs within this system.