Respiration

Respiration is achieved through the mouth, nose, trachea, lungs, and diaphragm. Oxygen enters the respiratory system through the mouth and the nose. The oxygen then passes through the larynx (where speech sounds are produced) and the trachea which is a tube that enters the chest cavity.

In the chest cavity, the trachea splits into two smaller tubes called the bronchi. Each bronchus then divides again forming the bronchioles. These bronchial tubes lead directly into the lungs where they divide into many smaller tubes which connect to tiny sacs called alveoli.

The average adult’s lungs contain about 600 million of these spongy, air-filled sacs that are surrounded by capillaries. The inhaled oxygen passes into the alveoli and then enters the capillaries (diffusion) into the arterial blood which is taken back to the heart for circulating around the body.

Meanwhile, the waste-rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when you breathe out.

Approximately 25% of the available oxygen in each breath is used, as our body can only cope with so much each time we breathe in.

Carbon dioxide and other non-essential gases are breathed out and the whole process is repeated between 10 – 20 times per minute for an average adult.