The Lungs

• Thorax

  the top part of your 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
• The lungs are surrounded by the pleural membranes
• The air that you breathe in goes through the trachea, which splits into 2 tubes called bronchi - one goes to each lung
• Each bronchi is called a bronchus
• The bronchi split into progressively smaller tubes called bronchioles
• The bronchioles end at small bags called alveoli where gas exchange takes place
• Oesophagus 


  food pipe
• trachea 


  windpipe
• intercostal muscle 


  the muscle between the ribs
• pleural membranes 


  the outermost layer of the lungs made up of 2 layers of membranes
• Alveoli

  small air sacs surrounded by a network of capillaries, 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 lots of 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 blood reaches the body cells, oxygen is released from the red blood cells (high concentration) into the body cells (low concentration)
• Carbon dioxide diffuses out of the body cells (high concentration) into the blood (low concentration), and is then carried back to the lungs
• breaths per minute = number of breaths/number of minutes