Nicotine

Smoking 3: Inhaling smoke

When you inhale smoke, it flows through your windpipe, or trachea, into your lungs. The trachea splits into two branches known as bronchi. In the lungs, the bronchi successively branch out to form tiny tubes, which end in clusters of small air sacs called alveoli.

The smoke containing nicotine, carbon monoxide and tar disperses through the air sacs after it is inhaled. Some of the tar attaches itself to the windpipe and the bronchi on the way.