How Do You Get Pneumonia?
Normally, all the germs in the air you breathe are trapped in the mucous layer lining your trachea, bronchi and bronchioles. The hair like structures called cilia constantly sweeps them upwards to your throat and the germs are expelled out by coughing.
Sometimes, the germs get passed your mucous and cilia and enter your alveoli. Normally, cells from your immune system attack these germs which keep them from making you sick.