The Lungs

• You need to get oxygen into your bloodstream to supply your cells for respiration. You also need to get rid of carbon dioxide from your blood. This all happens in your lungs when you breathe air in and out
• The lungs are in the thorax
• The thorax is the top part of the body
• The thorax is 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 goes in through the trachea. This spilts into 2 tubes called bronchi (each one a bronchus), one going to each lung

  
• The bronchi split into progressively smaller tubes calles bronchioles

  
• The bronchioles finally end at small bags called alveoli where the gas exchange takes place

  
• Alveoli carry out gas exchange in the body

  
• The lungs contain millions and millions of little air sacs called alveoli, surrounded by a network of blood capillaries. This is where gas exchange happens

  
• The blood passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains lot sof carbon dioxide and very little oxygen. Oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration). Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out
• When the blood reaches body cells oxygen is released from the red blood cells (where there's a high concentration) and diffuses into the body cells (where the concentration is low)
• At the same time, carbon dioxide diffuses out of the body cells (where there's a high concentration) into the blood (where there's a low concentration). It's been carried back to the lungs
• Example

  Ash takes 91 breaths in 7 minutes. Calculate his average breathing rate in breaths per minute

  > Breaths per minute = number of breaths / number of minutes

  = 91 / 7

  = 13 breaths per minute