Question

What can we understand by the line that in the respiratory system there is an extensive area of contact between the external environment and capillary blood vessels? What is external environment here?

Answer 1

Answer:

The main way the respiratory system protects itself is called the mucociliary escalator. From the nose through the bronchi, the respiratory tract is covered in the epithelium that contains mucus-secreting goblet cells. The mucus traps particles and pathogens in the incoming air.