Which of the following organs is NOT involved in the respiratory system?

The liver is not involved in the respiratory system. The primary function of the respiratory system is to facilitate the exchange of oxygen and carbon dioxide between the body and the environment, and the organs involved in this process include the trachea, lungs, and bronchi.

The trachea acts as a passage for air to enter and leave the lungs, while the bronchi are the main airways that branch off from the trachea and lead into each lung. The lungs are the primary organs where gas exchange occurs, allowing oxygen to be absorbed into the bloodstream and carbon dioxide to be expelled.

In contrast, the liver is part of the digestive system and plays a crucial role in processes such as metabolism, detoxification, and storage of nutrients. It does not participate in the mechanics of breathing or gas exchange, which is why it is not considered a component of the respiratory system.