When the whole body is irradiated, what area(s) is (are) considered the most radiosensitive?

The correct answer encompasses all the listed options—spleen, lymph nodes, and bone marrow—because these areas are particularly sensitive to radiation exposure due to their roles in the immune and hematopoietic systems.

The bone marrow is recognized as the most radiosensitive tissue, as it is responsible for producing blood cells, including red blood cells, white blood cells, and platelets. When exposed to radiation, the rapidly dividing stem cells in the bone marrow are significantly affected, leading to potential hematopoietic syndrome and a reduced ability to produce blood cells.

The spleen and lymph nodes are also crucial components of the lymphatic and immune systems. Both are involved in filtering blood and lymph, respectively, and in producing immune responses. Their cellular makeup, which includes lymphocytes and other rapidly dividing immune cells, makes them susceptible to the effects of radiation as well.

When considering overall radiosensitivity, it is essential to recognize how the damage to these organs could lead to serious health issues, including increased susceptibility to infections and impaired immune functions. Thus, all three areas listed are collectively acknowledged as the most radiosensitive parts of the body when it comes to whole-body irradiation.