How do pathogens exit the body?

Answer 1

The respiratory system is anatomically divided into two regions:
- The conductive region
- The respiratory region

The function of the conductive region is to lead fresh air into the lungs and out again when we exhale. This region includes the mouth, nose, trachea and upper parts of the lung-tree.
The respiratory region is where the gas-exchange itself happens and this includes the lower part of the bronchial tree.

Removal of pathogens:

In the conductive region pathogens are caught in mucus lining the inner surface. On the surface of the epithelia of the conductive region are so-called cilia, which are brush-like structures. These cilia will move the trapped pathogens upwards towards the pharynx, where it will be swallowed and eventually digested in the stomach.

In the respiratory region, however, there are no cilias. Instead pathogens are removed by alveolar macrophages (specialized immune-cells that digest pathogens). The macrophages can be found in the mucus lining the respiratory region.

The macrophages can travel two ways:
- to the conductive area, where cilias are present, and hereafter to the pharynx and stomach.
- they can wander through the alveolar epithelia towards the connecting tissue of the lungs. Here most are removed via lymfatic vessels to the lymphnodes of the region.

Answer 2

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