Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

Why is the branching of air passageways in the lungs significant?

1. It reduces air resistance.

2. It provides moisture for gas exchange.

3. It increases surface area for diffusion.

4. It filters dust particles from the air.

The correct answer is: It increases surface area for diffusion.

The branching of air passageways in the lungs is significant primarily because it increases the surface area available for diffusion. This extensive branching allows for the creation of numerous tiny air sacs called alveoli, which are where gas exchange occurs. The greater the surface area, the more oxygen can diffuse into the blood and carbon dioxide can be expelled from it. This is crucial for maintaining the efficiency of respiration, as it enhances the body's ability to meet its oxygen demands and remove waste gases effectively. While the reduction of air resistance and filtering of dust particles are important for maintaining respiratory health and effectiveness, the primary physiological role of the branching structure is to maximize the area for gas exchange. The provision of moisture is also a factor in respiration, but it does not directly pertain to the structural significance of branching itself. The key aspect here is the relationship between branching and the increased surface area, enabling the lungs to function optimally in gas exchange.