Why are the lungs and skin considered excretory systems?

While the skin is an excretory system, the lungs are not. The lungs are part of the respiratory system and are responsible for gas exchange, not excretion.

Skin as an excretory system:

The skin is an excretory system because it helps eliminate certain waste products from the body through sweat. Sweat contains water, electrolytes, and other substances that need to be removed from the body. When we sweat, these substances are released onto the skin's surface and eventually evaporate, taking the waste products with them.

Lungs as part of the respiratory system:

The lungs are part of the respiratory system and are responsible for gas exchange. They bring oxygen into the body and release carbon dioxide, a waste product of cellular respiration. However, the lungs do not directly excrete any other waste products; instead, they focus on facilitating the exchange of oxygen and carbon dioxide between the body and the external environment.