Which of the following is NOT a respiratory organ?

The heart is classified as a muscular organ responsible for pumping blood throughout the circulatory system, whereas the primary role of respiratory organs is to facilitate the exchange of gases—primarily oxygen and carbon dioxide—between the body and the environment. The pharynx, trachea, and lungs are all integral components of the respiratory system. The pharynx acts as a passageway for air, the trachea serves as the airway that connects the pharynx to the lungs, and the lungs are the organs where gas exchange takes place. Each of these structures plays a critical role in the process of respiration, whereas the heart, while essential to overall bodily function, does not participate in the respiratory process itself.