Internal circulation in the human body consists of two circulatory loops: the large circulatory loop and the small circulatory loop (pulmonary circulation). Gas exchange in the lungs occurs when blood circulates through the lungs, an important process to create oxygen-rich blood to supply the body's tissues and organs.

Bronchoscopy is a procedure to examine the inside of the bronchial tree using a bronchoscope. This is one of the techniques to help detect lung-related diseases.

Bronchial provocation test is a test to evaluate the responsiveness of the bronchial system to external factors. This is one of the bases used to diagnose asthma.