Which type of airway supplies air to a lobe of the lung?
a) primary bronchus
b) trachea
c) secondary bronchus
d) bronchioles
e) tertiary bronchus
The correct answer and explanation is:
Correct Answer: c) secondary bronchus
The secondary bronchus, also known as the lobar bronchus, is the airway that directly supplies air to a specific lobe of the lung. Each lung is divided into lobes. The right lung has three lobes—superior, middle, and inferior—while the left lung has two lobes—superior and inferior. For each of these lobes, there is a corresponding secondary bronchus.
The respiratory system starts at the trachea, a large airway that conducts air from the mouth and nose into the lungs. The trachea branches into two primary bronchi—one for each lung. These primary bronchi enter the lungs and then split into secondary bronchi. Each secondary bronchus enters a specific lobe of the lung and further divides into smaller tertiary bronchi, also called segmental bronchi. These then branch into even smaller tubes called bronchioles, which ultimately lead to the alveoli where gas exchange occurs.
The function of the secondary bronchus is to ensure that each lobe receives adequate airflow. By having one bronchus per lobe, the lungs can localize ventilation, which is important if a disease or obstruction affects a particular lobe. This structure also allows for more effective surgical interventions, such as lobectomies, where an individual lobe may be removed without disturbing the others.
To clarify the other options:
- The trachea is the main airway but does not supply individual lobes.
- The primary bronchus brings air to the lung as a whole, not specific lobes.
- Tertiary bronchi supply segments within each lobe, not entire lobes.
- Bronchioles are smaller branches that lead to alveoli but do not directly supply lobes.
Therefore, the secondary bronchus is the correct answer, as it is responsible for directing air into each lobe of the lung.