What organs do the respiratory system and cardiovascular system have in common?
Among the common organs of the respiratory and cardiovascular system are the lungs, as they are muscles that contract and expand as air moves through. The circulatory system primarily involves the heart, arteries, and veins which carry oxygenated blood that allow the lungs to operate, so there is an apparent connection.
The skin is often referred to as its own body system, but it can also be understood as part of both of the above, as it is the skin's epidermis that also regulates via perspiration/sweating to keep the body cool; the skin's layers also contains the muscles necessary for movement which operate on oxygen from the lungs. Exercise is the most strenuous version of this activity, to which greater lung capacity can be achieved via the increase of muscle mass, which is connected as well due to need for oxygen to work.