THE RESPIRATORY SYSTEM
This system consists of the lungs and air passageways. Its main role is to manage gas exchange, providing oxygen to the blood and disposing of carbon dioxide.

Inhaled air first moves into the nose and mouth before traveling through the pharynx (throat), larynx (the voice box where speech sounds are produced), trachea (windpipe), and bronchi (tubes that pass into the lungs).

In the lungs, the bronchial tubes divide into a vast network of smaller tubes that connect to tiny sacs called alveoli. The average adult's lungs contain about 600 million of these spongy, air-filled sacs, surrounded by capillaries.

Oxygen passing into the alveoli diffuses through the capillaries into the bloodstream. At the same time, waste-rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the opposite path out of the lungs during exhalation.