Which structure is NOT part of the respiratory system?

The liver is the structure that is not part of the respiratory system. Instead, it is an essential organ in the digestive system that plays a significant role in various metabolic processes, including the detoxification of harmful substances, production of biochemicals necessary for digestion, and regulation of blood sugar levels.

The respiratory system is primarily responsible for the exchange of gases—specifically, the inhalation of oxygen and the exhalation of carbon dioxide. Key structures of the respiratory system include the pharynx, which functions as a pathway for air to enter the lungs; the trachea, leading air into the bronchi and lungs; and the alveoli, which are tiny air sacs where gas exchange occurs. These components are vital in ensuring that oxygen is delivered to the bloodstream and that carbon dioxide is removed from the body efficiently.