A 54 year old man who is a farmer in rural Pennsylvania comes to GP because of a chronic cough. A chest x ray shows a mass lesion with hilar lymphadenopathy. Examination of tissue obtained on biopsy of mass shows multiple tiny oval forms within macrophages. 1. What is the likely diagnosis and why?

The main function of the respiratory system is gas exchange (O2 and CO2). Ventilation is the movement of air through the respiratory tract into (inspiration) and out of (expiration) the respiratory zone (lungs).