Final answer:
The right main bronchus is larger than the left main bronchus to accommodate the larger size of the right lung which has three lobes, compared to the smaller left lung with two lobes.
Step-by-step explanation:
The right main bronchus is indeed larger than the left main bronchus. The trachea bifurcates into the right and left bronchi as it descends into the lungs. This partitioning of the airway is vital for the separate ventilation of the right and left lungs. The right lung, being larger with three lobes, necessitates a wider right main bronchus to provide ample airflow. Conversely, the left lung is smaller due to the space occupation by the heart, thus having only two lobes and a comparatively narrower bronchus. The disparity in size between the two main bronchi is essential for the proper distribution of air into each lung's bronchial structure, consisting of secondary bronchi, tertiary bronchi, bronchioles, and eventually reaching the alveoli where gas exchange occurs.