The Lungs

• The thorax is the top part of your body. It's separated from the lower part of the body by the diaphragm.
• The lungs are like big pink sponges and are protected by the ribcage. They're surrounded by the pleural membranes.
• The air that you breathe in goes through the trachea. This splits into two tubes called bronchi (each one is a bronchus), one going to each lung.
• In the lungs, the bronchi split into progressively smaller tubes called bronchioles.
• In your lungs, the bronchioles end at small bags called alveoli where gas exchange takes place.
• The lungs contain millions and millions if little air sacs called alveoli, surrounded by a network of blood capillaries. This is where gas exchange happens.
• The blood passing next to your alveoli has just returned to your lungs from the rest of your body, so it contains lots of carbon dioxide and very little oxygen. So oxygen diffuses out of the alveolus, where there is a high concentration of oxygen, into the blood, where there is a low concentration of oxygen. Carbon dioxide diffuses out of the blood, where there is a high concentration of carbon dioxide, into the alveolus, where there is a low concentration of carbon dioxide, to be breathed out.
• After your blood has travelled to your lungs, it travels to your body cells. Once it has reached your body cells, oxygen is released from your red blood cells, where there is a high concentration of oxygen, and diffuses into your body cells, where there is a low concentration of oxygen.
• When your blood reaches your body cells in your circulatory system, whilst it releases oxygen, at the same time, carbon dioxide diffuses out of the body cells, where there is a high concentration of carbon dioxide, into the blood, where there is a low concentration of carbon dioxide. It is then carried back to the lungs.
• Kerry takes 91 breaths in 7 minutes. If you calculate her average breathing rate in breaths per minute the answer is 13 breaths/min because 91/7 = 13 breaths/min.