What does the respiratory system primarily consist of?

The respiratory system primarily consists of the nose, mouth, trachea, bronchi, and alveoli because these structures function together to facilitate the process of gas exchange in the body. The nose and mouth serve as entry points for air, while the trachea acts as the airway that conducts air into the lungs. The bronchi branch out from the trachea and lead into each lung, allowing air to flow into the bronchial tubes. Finally, the alveoli are tiny air sacs where the actual exchange of oxygen and carbon dioxide takes place in the bloodstream. This intricate arrangement ensures that oxygen is efficiently taken in and carbon dioxide is expelled, which is essential for maintaining respiratory health and overall bodily function.

The other options present systems or components that do not belong to the respiratory system. The heart and blood vessels are primarily associated with the circulatory system, muscles and tendons are part of the muscular system, and bone and cartilage belong to the skeletal system, each serving distinct and vital functions that support the body as a whole.