1. Structure and function of the respiratory system

2. Functions of the respiratory system
The respiratory is the breathing mechanism of the body. It includes the mouth, nose, larynx voice box), trachea (wind pipe), lungs, diaphragm, intercostal muscles and the thoracic cage (rib cage).
The respiratory system helps the body take in oxygen and remove carbon dioxide and heat.

3. Structure of the respiratory system

4. Passage of oxygen through the body
When we breathe in, oxygen comes in through the nose and mouth. Air comes down the trachea and enters the bronchi, the main tubes that branch off the windpipe into each lung. The bronchus goes through all the lobes of the lung, and branches out like an upside-down tree into smaller bronchioles which divide into tiny alveolar sacs and alveoli. These air sacs allow oxygen and other nutrients to change places.

5. Gaseous exchange
The method by which oxygen and carbon dioxide change places is called gaseous exchange. These gases can only change places through the process of diffusion. This is where a high concentration of gas moves to a low concentration of gas. The exchange of these gases occurs in the capillary network.

6. Capillary network
The high concentration of oxygen found in the alveoli during inspiration (breathing in) moves to the smaller vessels of the pulmonary vein. This is so that blood can take oxygen to the heart for distribution. The high concentration of carbon dioxide in the smaller vesels of the pulmonary artery moves to the alveoli, so that it can be removed during expiration (breathing out)

7. Mechanics of breathing
Inspiration
During inspiration the lungs need to expand so they can hold more air. In order to make room for the lungs to do this, the diaphragm contracts and the ribs move up and out due to the contraction of the intercostal muscles.
Expiration
During expiration, the lungs slightly deflate; when this happens do not take up as much room and so the ribs can move downwards and inwards and the diaphragm can relax. This helps the lungs to expel some of the air inside them.

8. Key terms TERM DESCRIPTION Breathing frequency
The amount of breaths per minute
Tidal volume
The volume of air breathed in or out per breath
Minute ventilation
Minute ventilation the volume of air breathed per minute
Vital capacity
Maximum amount of air that can be forcibly inhaled and exhaled In one breath
Total lung capacity
All the air in the lungs after a maximum inhalation
Residual lung volume
The amount of air left in the lungs after a forced breath out