Which of the following is NOT a component of the respiratory system?

The heart is not considered a component of the respiratory system; it is part of the circulatory system. The primary function of the respiratory system is to facilitate the exchange of gases (oxygen and carbon dioxide) between the body and the environment. Key components of the respiratory system include the trachea, bronchi, and lungs, all of which play essential roles in the process of breathing and gas exchange.

The trachea serves as the airway that directs air into the bronchi, which then branch into the lungs. The lungs are the organs where the actual exchange of gases occurs, allowing oxygen to enter the bloodstream and carbon dioxide to be expelled.

In contrast, the heart functions to pump blood throughout the body, ensuring the transportation of oxygen-rich blood to tissues and organs. While the heart and respiratory system work closely together in maintaining proper oxygen levels and removing carbon dioxide, the heart itself does not belong to the respiratory system.