Gaseous Exchange

• Key info

  • The heart pumps blood to the lungs , via the pulmonary artery, where it collects oxygen 
  • The oxygenated blood then returns to the heart , and the heart pumps it around the whole body where it delivers oxygen to the body cells
• Describe the passage of air through the lungs

  • Air passes into the lungs through a tube called the trachea , which contains rings of cartilage to prevent it from collapsing during inhalation 
  • The trachea splits into 2 smaller tubes called bronchi , which divide into many smaller tubes called bronchioles further into the lungs, and these end in tiny air sacs called alveoli 

  
• What are alveoli, and what is there function

  • Alveoli are tiny air sacs
  • They are where gasses diffuse in and out of the bloodstream

  
• Describe the process of gaseous exchange in the alveoli

  • In the alveoli, oxygen from the air diffuses into the bloodstream 
  • Carbon dioxide diffuses out of the bloodstream back into the air

  
• What are the adaptations of the alveoli that allows it to be efficient at exchanging oxygen and carbon dioxide

  • There are millions of alveoli, and they all have a large,  moist surface area 
  • The alveoli have very thin walls and are very close to the capillaries , so the diffusion path is very short 
  • The alveoli have a very rich blood supply

  
• What happens after gas exchange takes place in the alveoli

  • Once the oxygen diffuses into the blood , it is rapidly removed - this ensures that the concentration gradient is as steep as possible 
  • The blood is then taken back to the heart through the pulmonary vein

  
• How does breathing increase the rate of diffusion

  • Breathing brings fresh oxygen into the alveoli and takes away the carbon dioxide 
  • This makes the concentration gradient for these gases high 
  • This increases the rate of diffusion