Anatomy and functions

Anatomy and functions

Our body depends on a constant supply of oxygen. Humans can live a few weeks without eating, a few days without drinking but only a few minutes without breathing. The respiratory system draws air into the body, takes oxygen into the bloodstream and removes the carbon dioxide - the body's "exhaust gas".

The anatomy of the respiratory system can be divided into two main sections: the upper and lower respiratory tract. The nose, mouth and throat are all parts of the upper respiratory tract. The lower respiratory tract is composed of the windpipe (the trachea), which divides into the bronchi, which in turn divide into smaller and smaller tubes called bronchioles. These end in tiny balloon-like air sacs called alveoli.

The oxygen that we inhale transfers into the blood stream in the thin-walled alveoli, via millions of tiny blood vessels (capillaries) that are wrapped around each of the alveoli. In exchange, carbon dioxide is transferred out of the blood steam and exhaled each time we breathe out. There are around 300 million alveoli in the average adult respiratory system, creating a total surface area of 70 - 80 square metres for the essential process of gas exchange.