Category talk:Body systems

What qualifies as a Body System?
I'm confused about this category. I thought that a "Body System" referred to something like the cardiovascular system, nervous system, immune system, etc. But I've noticed that this category is being used for almost anything in the body. Perhaps many of these items belong in subcategories of "Body System"? E.g. Immune cells would be in the "Immune System" category, not the "Body Systems" category. Pyrrhus (talk) 18:39, 26 March 2019 (EDT)