Digestive 
Blood
Cardiovascular
Dermatology
Genitourinary,
Hormones
Infections
Oncology and
Musculo-skeletal
Mental health and
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Respiratory
Senses
Various
When we breathe, air moves through the bronchi, the bronchioles and inside the alveoli.
From the alveoli, oxygen goes into your blood while carbon dioxide is expelled. When you have pneumonia, the alveoli become inflamed (irritated and swollen) and fill with fluid, so that it becomes difficult to breathe.
