Final answer:
The respiratory pathways from the trachea to the alveolar sacs involve a hierarchy of air tubes: the primary bronchi, secondary bronchi, tertiary bronchi, and bronchioles. These structures facilitate the flow of air to the alveoli where gas exchange with blood occurs.
Step-by-step explanation:
The respiratory system is composed of several structures through which air passes before reaching the alveoli, where gas exchange occurs. From the trachea, air moves into large air tubes known as the primary bronchi (singular, bronchus). Each bronchus then divides into smaller secondary bronchi, and these subdivide into smaller tertiary bronchi. Tertiary bronchi continue to branch into even smaller tubes called bronchioles. The bronchioles eventually lead to alveolar ducts, which end in clusters of air sacs known as alveolar sacs. Within these sacs are numerous individual alveoli, where the actual gas exchange with the blood takes place.
Therefore, the four progressively smaller air tubes that connect the trachea and the alveolar sacs are the primary bronchi, secondary bronchi, tertiary bronchi, and the bronchioles. Lastly, the alveolar ducts connect the smallest bronchioles to the alveolar sacs. This organization ensures air is warmed, moistened, and filtered before reaching the alveoli.
The four air tubes connecting the trachea to the alveolar sacs in sequence are the primary bronchi, secondary bronchi, tertiary bronchi, and bronchioles. These structures ensure delivery of air to the alveoli for efficient gas exchange with the blood.