A new study from UC San Francisco suggests that the lungs do more than just take in oxygen and release CO2 from the blood. The study found that in mice, their lungs produced about half of their total platelets. This makes sense because the lungs are connected to the circulatory system, and are where oxygenated blood originates and goes out to the rest of the body. If your body needs to get platelets somewhere fast, it makes the most sense that this would be their origin. The researchers also found that there are actually stem cells in the lungs that end up becoming blood cells. These stem cells were thought to only be found bone marrow up until now. These findings are still not yet proven to be true for humans, but have been proven true in mice. They have similar biological features as humans, so it is quite possible that these findings are also true in humans, but further testing is being done to prove this.